You have just learned that a parent or older relative left a will giving most of the estate to one heir. The signature does not look like the one you remember, or the will was made a few weeks before death while the person was seriously ill. Doubts like this arise in many families, but doubt alone does not persuade a court to revoke a will, and accusing a relative without evidence divides the family needlessly.
This guide takes only the angle of the heir who doubts a will: what to check, what evidence to gather and how much time there is. For the general rules on who the heirs are and how an estate is administered, see the main inheritance guide. For drafting a sound will and choosing an executor, see choosing an executor in a will. For wills involving foreigners, see wills and inheritance for foreigners.
The short answer
Check four things in order: whether the will is in a valid form; whether the testator had the legal age and capacity when making it; whether the signature and document are the testator's own; and whether duress, fraud or mistake was present. Each rests on different rules and different time limits, and one of those limits is very short and runs from the day you know.
The rule. Sections 1656 to 1663 of the Civil and Commercial Code set the forms of will: ordinary (1656), holographic (1657), public document (1658), secret document (1660) and oral (1663). Section 1670 bars minors, persons of unsound mind or quasi-incompetent, and persons who are deaf, mute or blind in both eyes from acting as witnesses. Section 1653 provides that the writer of a will, a witness to it, and the spouse of either cannot take property under that will. Section 1705 makes a will, or a clause in a will, void if it breaches section 1652, 1653, 1656, 1657, 1658, 1660, 1661 or 1663. Sections 1703 and 1704 deal with the testator's age and capacity, sections 1708 and 1709 with duress, fraud and mistake, and section 1710 with the time to sue. An heir who forges or conceals a will may be excluded under section 1606.
Our practical view. Do not start with an accusation. Start by asking to see the original and gathering evidence quietly, by lawful means. Three facts, namely who drafted the will, who was in the room and what the testator's condition was that day, often decide a case more than a feeling that the handwriting looks wrong. A will with a defective form can fall on the document alone. Duress or lack of awareness needs witnesses and medical records, and the outcome depends on the facts and the court's discretion.
Hypothetical example. Mr Thong, 82, lived in Khon Kaen and had three children: Nida, Somchai and Pranee. After he died, Somchai, who had lived with him throughout, produced a will leaving the house and land to him alone. It was dated 12 days before Mr Thong entered hospital for the last time. Nida thought the signature slanted differently from what she remembered, and the will had only one witness, a neighbour of Somchai. Nida asks what to do first. We use this example throughout.
1. What forms can a will take, and which fail most easily?
Thai law does not accept every kind of will. It must follow a prescribed form, otherwise it is void under section 1705.
| Form | Section | Key requirements |
|---|---|---|
| Ordinary | 1656 | In writing, dated; testator signs in the presence of at least two witnesses present together; witnesses sign to certify at that time. Deletions and additions must follow the same form |
| Holographic | 1657 | Testator writes the whole text, date and signature by hand; no witnesses needed. Any change must be made by the testator and signed |
| Public document | 1658 | Declared to the district registrar before at least two witnesses present together; official writes it down, reads it aloud, all sign; official dates and seals it |
| Secret document | 1660 | Testator signs, seals, signs across the seal, presents it to the district registrar and at least two witnesses, who sign the envelope |
| Oral | 1663 | Only in special circumstances such as imminent danger of death; declared to at least two witnesses together, who must then report promptly to the district office |
The ordinary form draws most disputes because it needs complete witnesses signing at the same time. Points to check:
- Number and identity of the witnesses. Were there really two, and who were they? Witnesses must see the testator sign, not sign afterwards.
- Witnesses certifying the signature, as section 1656 requires, rather than merely signing to say they knew of it.
- Witness qualifications under section 1670. Minors, persons of unsound mind or quasi-incompetent, and persons who are deaf, mute or blind in both eyes cannot act.
- A witness or writer who benefits. Section 1653 provides that the writer of the will, a witness to it, and the spouse of either cannot take property under that will, so a clause giving them property is void under section 1705.
- The date. Day, month and year must be present when the will is made.
- Alterations. Erasures or additions not signed in the required way leave that part ineffective.
For a public-document will, the district office that took it will hold a record. For a holographic will, the whole must be in the testator's own hand, not typed. If any part was typed or written by someone else, check whether it satisfies section 1656.
2. Did the testator have the age and capacity?
Section 1703 makes a will made by a person under fifteen full years void. Section 1704 has two limbs.
- Court has declared the person incompetent: a will made is void.
- Person alleged to be of unsound mind, no court order: the will fails only if it is proved that the testator was of unsound mind when making it.
The burden therefore falls on the person alleging unsoundness at the time. Serious illness, old age or dementia in general is not enough; you must show that on the day of the will the testator could not understand what they were doing. Useful evidence includes medical records close to the date, psychiatric or neurological assessments, nursing notes, medication lists, and testimony from doctors, nurses or anyone who saw the testator that day.
The other side may use the same records. A sick person with lucid intervals can make a will, and a treating doctor's note that the patient was alert that day supports the will. Be ready for the evidence to point either way.
In the example, Nida should find out where Mr Thong was on the date of the will, what treatment he was receiving and who took him there. She should not rely on relatives' accounts alone.
3. Is the signature really the testator's?
This is forgery proper: the deceased did not make the will or sign it. A will the deceased did not make does not reflect their intention, and forging a will is a criminal offence.
What to do:
- Ask to see the original, not a copy. A photocopy limits what can be checked about handwriting and ink.
- Collect comparison signatures from around the same period, such as bank documents, contracts and receipts signed by the deceased, ideally undisputed genuine ones.
- Do not touch, alter, mark or photograph the original in a way that damages it. If someone else holds it, ask through a lawyer or when it is presented to the court.
- Have it examined by an expert. Document and signature examination can be done by state forensic units or by an expert requested by the court or a party. The result is an expert opinion that the court weighs with other evidence, so it does not always settle the case.
- Ink, paper and writing sequence. In some cases an expert can tell whether text was added later.
Caution: the signature of an elderly or ill person often changes with their physical condition, so a difference alone is not proof of forgery. Comparison samples from a similar time are needed.
4. Duress, fraud and mistake: how do they differ?
This differs from forgery because the testator really signed, but the intention was not free.
- Duress (section 1708). After the testator's death, an interested person may apply to the court to revoke a will made under duress. The application cannot be made if the testator lived more than one year after the duress ended.
- Fraud or mistake (section 1709). Revocation is available only if the mistake or fraud was such that without it the will would not have been made, and this applies even if the fraud came from someone other than the beneficiary. A will made by mistake or fraud takes effect unless the testator revokes it within one year of learning of the matter.
Ordinary family pressure, such as pleading, persuasion or close caregiving, is not always duress. The court must see fear or deceit serious enough that the testator made a will they did not want. Facts that often matter:
- Who contacted the lawyer or drafter, and who paid
- Whether the beneficiary was in the room, or took the testator there
- Whether the testator was isolated from other relatives before or after
- Whether the content matches what the testator had said or done, or departs sharply from earlier plans
- Whether the testator told witnesses or close people they were unwilling, and whether messages, voice notes or records exist
5. Does an heir who forges or hides a will lose the right to inherit?
Section 1606 lists unworthy heirs. The relevant limbs are:
- (4) a person who, by fraud or duress, caused the deceased to make, revoke or change a will, in whole or in part, concerning estate property, or prevented them from doing so
- (5) a person who forges, destroys or conceals a will, in whole or in part
The deceased may lift the exclusion by forgiving in writing. The effect is that the heir is excluded from the estate, but the court decides on the evidence. This guide does not say which facts will fall within the section, and it should not be used as a threat in negotiation.
6. Criminal penalties, and when to go to the police
Section 266 of the Criminal Code covers documents where forgery carries a heavier penalty, including wills: imprisonment of one to ten years and a fine of THB 20,000 to 200,000. Section 268 punishes using or relying on a document made by an offence under sections 264 to 267 at the penalty of that section, and if the user is the forger, a single penalty under section 268 applies (second paragraph). Sections 264 and 265 cover ordinary forgery and forgery of documents of right or official documents.
The criminal and civil tracks are separate. A police complaint does not stop the clock on the civil action to revoke the will, so do not wait for the criminal outcome before taking civil advice. And do not file a complaint with nothing to support it: if the accusation is untrue, the complainant may be liable. Have a lawyer assess the evidence first.
7. Time limits
This table summarises the limits that bear on doubting a will. Have a lawyer check your actual dates.
| Matter | Time limit | Section |
|---|---|---|
| Action to revoke a testamentary provision (for example duress, fraud, mistake), plaintiff knew the ground in the testator's lifetime | 3 months after the testator's death | 1710 (1) |
| Same, other cases | 3 months from when the plaintiff knew the ground | 1710 (2) |
| Plaintiff did not know of a provision affecting their interest | 3 months from when they knew or should have known | 1710, final paragraph |
| Outer limit for an action to revoke | Barred after 10 years from the testator's death | 1710 |
| Application to revoke for duress | Not allowed if the testator lived more than 1 year after the duress ended | 1708 |
| Will made by mistake or fraud | Takes effect unless the testator revokes within 1 year of learning | 1709 |
A claim to a share of the estate generally also engages the estate limitation in section 1754, which we explain in the main guide, with a 1-year period from knowledge and a 10-year outer limit from the death. Which one applies to your case depends on the facts. Treat the 3 months under section 1710 as the date to worry about most until a lawyer confirms otherwise.
8. Evidence to gather
| Evidence | Where from | What it proves |
|---|---|---|
| Original will, envelope or related files | The holder, the executor or the court where it was filed | Form, signature, alterations |
| A will kept at the district office | The district office that took the public or secret will | That it was made in the proper form, and who the witnesses were |
| Comparison signatures | Bank papers, contracts and certificates signed by the deceased | Expert comparison |
| Medical records and treatment notes | Hospital, clinic, regular doctor | Capacity and state of mind on the date |
| List of witnesses and people present | The will itself, relatives, neighbours, carers | Who saw the signing, who was there |
| The drafter | Lawyer or typist, receipts, chats, emails | Who instructed, who paid, from whose information |
| Messages and notes before and after | Documents or chats you are lawfully entitled to access | The deceased's intentions and any change |
Do not access the phone, email, bank account or social media of the deceased or any relative without permission, even if you expect to find evidence. Unauthorised access to a computer system can be an offence under sections 5 to 7 of the Computer Crime Act B.E. 2550 (2007), and personal data is protected by the Personal Data Protection Act B.E. 2562 (2019). If you need records held by a bank or hospital, ask through an heir who is entitled or use a court process.
9. Sample letter requesting a copy of the will and its circumstances
Send this to the person holding the will or to the executor. It is a courteous first step and not an accusation (example only; adapt it to your facts).
Subject: Request for a copy of the will and details of its making - Mr Thong ____
To: Mr Somchai ____ (holder of the will)
I, Ms Nida ____, am a child of Mr Thong ____, who died on ____.
I understand that a will dated ____ exists and I have an interest in the estate.
So that all heirs have the same information, I ask for your cooperation as follows:
1) A complete copy of the will, every page, and an appointment to inspect the original
2) The names and addresses of the witnesses to the will
3) The name of the person who drafted it and the place where it was made
4) Where the will has been kept since it was made
Please reply within ____ days of receiving this letter at ____.
I ask that the original be preserved as it is, and that nothing be altered, crossed out or transferred under the will until the heirs have been able to check it.
This letter is not an accusation, and I reserve all my rights.
Yours sincerely,
Ms Nida ____ Date ____
Send it by a method that leaves proof, such as registered post with acknowledgment of receipt, or a message you screenshot, and keep a copy. If the other side refuses or stays silent, ask a lawyer about applying to the court for the will to be opened or the original produced. If no administrator has been appointed, see filing the court petition for an estate administrator, and if an administrator is silent, see an estate administrator who will not distribute or respond.
10. Do not accuse relatives in public
Posting online, writing in the family chat or telling the village that a sibling forged the will could expose you to a defamation claim and makes settlement harder. Speak only to your lawyer, the heirs directly concerned and officials who have a duty to act. Verifiable statements such as "I have asked to see the original" are safer than conclusions such as "it is forged".
11. Checklist
In the first week
- Note the date of death, the date you learned of the will and the date you learned the ground for your doubt
- Ask to inspect the original and obtain a copy of every page
- Photograph every page without touching or changing the original
- Send the request letter and keep proof of delivery
- Ask a lawyer about the three-month limit under section 1710
Check form and capacity
- Identify the form: 1656, 1657, 1658, 1660 or 1663, and whether it complies
- Check the number, identity and qualifications of the witnesses under section 1670, and whether a witness or the writer of the will (or their spouse) is a beneficiary (section 1653)
- Check the date, alterations and initials
- Request medical records near the date, through an entitled person or the court
Signature and circumstances evidence
- Collect comparison signatures from a similar period
- Note the witnesses, the drafter and who was in the room
- Keep messages and documents you can lawfully access; do not enter anyone's accounts or devices
- Check the district office if it was a public or secret will
Approach and communication
- Do not accuse relatives in public or in chat groups
- Do not threaten a police complaint to bargain over shares
- Have a lawyer assess the evidence before suing or filing a complaint
Further reading
- Parents have died: how is the estate divided? — order of heirs, administrators and the general estate limitation
- Choosing an executor in a will — who may be an executor and what the duties are
- Wills and inheritance for foreigners — when a will involves foreigners or assets in several countries
- Filing the court petition for an estate administrator — the court steps when an administrator is needed
- Estate administrator who will not distribute or respond — when the administrator is silent
- Estate assets found after distribution — assets that surface later
Turn doubt about a will into questions that can be checked: is the form valid, did the testator have capacity, is the signature genuine, and was there duress or fraud. Write down the date you learned each fact, because the three-month limit in section 1710 is very short.
We help heirs examine a will, gather evidence and assess whether to sue to revoke or to negotiate. For an initial consultation, call +66 92 254 2045 or send us the details. See also our estate practice and civil litigation practice.
This guide is published by Suwanvara Law Firm — a Khon Kaen law firm established in 1986. General information only, not legal advice on a specific matter.
