Thai and English Versions of a Contract Say Different Things: Which One Prevails, and What to Check Before Signing

The core answer

There is no ready-made answer that the Thai or the English version always wins. The first thing a court looks at is whether the contract itself addresses the question. A governing-language (prevailing-language) clause is the strongest starting point because the parties agreed it. But such a clause has limits, and it often fails to protect annexes, purchase orders, quotations, or later amendments made in only one language.

With no clause, the court applies the general rules. Civil and Commercial Code section 171 directs attention to the true intention rather than the wording, and section 368 requires contracts to be interpreted in good faith with regard to usual custom. So the court reads the whole contract, the drafts exchanged, and how the parties actually behaved, not just the conflicting clause. A foreign-language document put before a Thai court may have to be accompanied by a Thai translation (Civil Procedure Code section 46).

The safest approach is to avoid a mismatch before signing: pick one master language, run a back-translation check, build a defined-terms table, and use identical clause numbering.

1. How does a governing-language clause work?

The clause says which version controls if the two conflict, for example: "This agreement is made in two languages. If they conflict, the English version prevails." It reduces argument, but check these weak points.

• The clause appears in only one version. If it is only in the English text and the Thai text the other side signed lacks it, or says the opposite, it is unclear whether the clause binds and what each party understood.
• It covers only the body of the contract. Annexes, price schedules, statements of work, purchase orders and quotations may be separate documents. A clause referring to "this agreement" may not reach them.
• Later amendments in one language. An amendment made in English only, while the Thai text of the original is not amended, makes the versions drift apart without anyone intending it.
• It does not choose the language of the court. Choosing the English version does not make a Thai court conduct proceedings in English. A Thai translation is still needed (see section 3).
• Loose wording. "The English version prevails for interpretation" and "the English version governs" can lead to different results when the Thai text contains a right or duty absent from the English.

Even a clear clause does not always make a court blind to the parties' real intention. The court still interprets under sections 171 and 368 what the parties meant the clause to do, so the clause must be clear and the parties' conduct must not contradict it.

2. With no clause, what does the court do?

The court starts from three sections of the Civil and Commercial Code.

• Section 171: in interpreting a declaration of intention, regard the true intention more than the words or letters.
• Section 368: a contract is interpreted in accordance with the intention in good faith, with regard to usual custom.
• Section 11: in case of doubt, interpret in favour of the party who would bear the obligation.

Supreme Court judgment no. 3416/2566 (B.E. 2566 / 2023) holds that interpretation must follow the understanding of both parties, that one party's intention alone cannot be adopted, and that true intention under section 171 outweighs the wording. It concerned a settlement agreement, not a bilingual contract, but the interpretive principle is the same.

When two versions conflict, courts typically ask the following. These are observations from the interpretive method, not a statutory list.

• What do the drafts and emails exchanged during negotiation show was agreed?
• Which version did both sides actually read and negotiate from?
• Who drafted and translated, and did the difference come from a translation error or a deliberate edit?
• How did the parties perform before the dispute, for example when they paid and delivered?
• Read with the rest of the contract, which version is more consistent with the other clauses?

If doubt remains after all of that, section 11 is the last resort: interpret in favour of the party who bears the obligation, such as the one who must pay or be liable. Supreme Court judgment no. 6232/2564 (B.E. 2564 / 2021) involved a guarantee whose own terms conflicted, and the court read it in the guarantor's favour. It was not a bilingual contract, but it shows that where wording conflicts, the cost can fall on the party who drafted it badly. Outcomes depend on the facts of each case.

3. Does an English document need a translation in a Thai court?

Civil Procedure Code section 46 provides that the court's proceedings are conducted in Thai, and pleadings and documents in the case file must be written in Thai. Where the original of a document submitted to the court is in a foreign language, the court orders the submitting party to provide a translation of the whole document or of the important parts, with a certification filed together with the original.

Supreme Court case law suggests practice is not rigid.

• No. 3924/2551 (B.E. 2551 / 2008): an English contract attached to the complaint with a translation and relied on as evidence was properly part of the record, and the court had power to admit it.
• Nos. 4725/2565 and 5554/2561 (B.E. 2565 / 2022 and 2561 / 2018): submitting a foreign-language document to the court does not always require a Thai translation unless the court orders one.

Practical conclusion: if an important contract is in English, prepare a certified Thai translation before suing or answering a dispute. When each side's translation differs, the translation becomes a second dispute. An expert translation with certification is useful before signing too. See notarisation and translation.

4. Four kinds of mismatch (hypothetical examples)

These are invented scenarios to illustrate risk, not real cases.

4.1 Payment date. The English text says "payment within 30 days" without saying from when. The Thai text says "within 30 days from receipt of the invoice". The seller sends the invoice 20 days after delivery. The buyer relies on the Thai text and says payment is not yet due. The seller relies on the English text and claims default interest. The questions are how the parties performed before and what the negotiation drafts said about the start of the period.

4.2 Scope of work. The English text says "supply and installation of equipment". The Thai text says only "supply of equipment", and "including installation" has dropped out. The contractor claims extra for installation. The client says the price already covers it. The issues are whether the quotation and drawings priced installation in and who proposed the wording.

4.3 Penalty rate. The English text sets a penalty of 0.1 percent of contract value per day. The Thai text says 1 percent per day, ten times more. The customer deducts at the higher rate. Under section 379 a contractual penalty is forfeited when the debtor defaults, and section 383, first paragraph, lets the court reduce it to a reasonable amount if disproportionately high, considering every lawful interest of the creditor. But once paid, the right to seek reduction is lost, so do not pay at the high rate without reserving your rights. See a customer deducts penalties or damages from payment.

4.4 Termination. The English text requires 30 days' notice. The Thai text requires 60. One party gives notice, stops performing after 30 days, and the other says the termination was invalid and claims damages for the rest of the period. The risk is that the party who acted early becomes the party in breach.

5. Table: mismatch type, risk and fix

6. Annexes, purchase orders and quotations that slip through review

The main contract often gets a bilingual check but the documents used daily do not: a purchase order sent in English by a foreign customer, a quotation prepared in Thai by sales, and terms printed behind a purchase order. They may carry payment terms, penalties and cancellation rights that differ from the main contract. If the main contract does not set an order of precedence, a dispute arises over which document applies.

To reduce the risk, state in the main contract which documents form part of it, which prevails in a conflict, and that a purchase order cannot change the main terms unless signed in writing by an authorised person. See contract review without a legal department.

7. Review process for a bilingual contract before signing

1. Choose one master language. Draft and negotiate in it, then translate. Do not let each side draft separately in its own language.
2. Put a governing-language clause in both versions and word it to cover annexes and amendments.
3. Back-translate. Have someone else translate the Thai text back into English without seeing the original, then compare. The differences mark the risk points.
4. Make a defined-terms table in both languages, for example "business day", "indirect loss", "confidential information", and follow it throughout.
5. Use the same clause numbers. Clause 7.2 in Thai should match 7.2 in English so they can be compared and cross-referred.
6. Check numbers and dates separately: amounts, percentages, days, and the Buddhist Era versus Gregorian year (for example 2569 and 2026).
7. Check annexes and attachments exist in both languages and cite the correct clauses.
8. Sign both versions and keep them as one set, with dated, versioned files.

If you want a lawyer to review the bilingual contract before signing, see contracts and documents.

8. What to do once a dispute has arisen

• Preserve everything: signed versions, every draft round, negotiation emails, chat messages and purchase orders. Do not edit or overwrite original files.
• Build a clause-by-clause comparison showing where the texts differ and how much money or what right is affected.
• Check the governing-language clause: whether there is one, in which version, and which documents it covers.
• Look at past conduct: which version the parties followed, since it may be evidence of true intention.
• Do not act alone before analysis: stopping payment, stopping work or terminating, because a wrong reading can make you the party in breach.
• Reserve rights in writing if you must pay or perform in the meantime, stating that you do so without waiving the right to dispute.
• Prepare a certified translation in case you need to file it in court.
• Reply to demand or breach letters carefully. See received a breach-of-contract letter.

9. Common mistakes

• Believing the English version always wins, or the Thai version always wins, without looking at the clause and the true intention.
• Letting sales staff or translators produce each version with no one comparing them.
• Using machine translation and signing without checking figures, dates and legal terms.
• Amending one version by an amendment and not the other.
• Letting purchase orders or quotations carry terms that conflict with the main contract, with no order-of-precedence clause.
• Signing on the assumption that a court will reduce an excessive penalty, when that is discretionary and not guaranteed.
• Paying the high penalty rate without reserving rights, then losing the right to seek reduction under section 383.
• Giving notice of termination on the period in the version you read, without checking the other.

10. Checklist before signing and after a dispute arises

• One master language chosen; governing-language clause in both versions
• The clause covers annexes, attachments and amendments
• Back-translation done and differences fixed
• Bilingual defined-terms table made
• Clause numbers match; figures, dates, periods and penalty rates match everywhere
• Termination notice period and method of notice match
• Purchase orders, quotations and statements of work have an order of precedence
• Both versions signed and kept as one set
• Once a dispute arises, drafts, emails and original files preserved
• Comparison table made before responding
• Rights reserved in writing if paying or performing meanwhile
• Certified Thai translation ready in case of court filing

Further reading

• Contract review before signing when you have no legal department — an internal review and approval process
• A big customer sent us its contract — contracts drafted by the other side
• When a customer deducts penalties or damages from its payment — penalties and court reduction
• Signing company contracts online — signing and keeping evidence of both versions
• Received a breach-of-contract letter? — when a dispute begins

A governing-language clause helps only when it is written clearly and covers the whole document set, but preventing the two versions from conflicting before signing is cheaper and more certain than proving intention in court.

We help review bilingual contracts, compare the texts clause by clause, draft governing-language and order-of-precedence clauses, and assess options when a dispute over mismatched versions arises. For an initial consultation, call +66 92 254 2045 or send us the details. See also contracts and documents and notarisation and translation.

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.