An affidavit of foreign law is a sworn, written statement prepared by a qualified person that explains the content, scope and application of foreign legal rules for the benefit of a Thai court, administrative body, or other decision-maker. In cross-border litigation, probate, family law matters, corporate disputes, or administrative proceedings where foreign law determines rights or the validity of acts, Thai judges commonly require authoritative proof of the foreign law. Because Thai tribunals have no judicial notice of foreign statutes or foreign case law, a properly drafted, evidenced and authenticated affidavit of foreign law is often decisive.
Why Thai proceedings need an affidavit of foreign law
Thai courts apply Thai procedure to resolve factual questions, but when an issue turns on what a foreign rule actually is (for example, the validity of a foreign marriage, the content of foreign insolvency law, or foreign corporate formation rules), the foreign rule is a matter of fact to be proved by evidence. An affidavit of foreign law gives the court a concise, sourced statement of the relevant foreign rules and authorities and an expert’s application of those rules to the facts of the case. Without it, the Thai court may make assumptions, require additional proof, or delay the case while foreign law is proved orally.
Who should prepare the affidavit
Best practice is to instruct an independent expert on the foreign law — typically a lawyer admitted in the foreign jurisdiction, an academic who specializes in the area, or an accredited practitioner with demonstrable expertise. The affidavit should be prepared and sworn by that expert. In some cases counsel in Thailand will prepare a supporting affidavit that summarizes the expert evidence and attaches the expert’s sworn statement as an exhibit, but courts generally prefer direct expert affidavits from the foreign-law specialist where possible.
Core contents and structure
A persuasive affidavit of foreign law follows a clear, traceable structure:
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Title and identity clause — the deponent’s full name, professional qualifications, practicing address, admission/registration details (bar number or academic post), and a brief CV showing competency in the relevant field and jurisdiction.
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Instructions and documents relied on — a short statement of the instructions received, the questions posed by counsel, and a list of primary and secondary materials relied upon (statute provisions, case citations, textbooks, government guidance). Each primary source should be annexed and paginated.
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Questions of law addressed — the affidavit should set out the discrete legal questions it answers (e.g., “Whether under English law a foreign divorce obtained in X circumstances is effective for the purpose of marriage capacity in domestic proceedings?”). Precise questions limit scope and make the opinion useful.
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Statement of foreign law — a reasoned exposition of the relevant foreign statutory rules, definitions, case law authorities and prevailing judicial interpretation. Where possible, cite leading cases with neutral citation numbers and paragraph references; explain any divergent authority.
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Application to facts — apply the stated law to the material facts of the case and give a reasoned conclusion that directly answers the question(s) posed.
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Oath / attestation paragraph — a sworn declaration confirming the truth of the statements and signed before a competent notary or authorized official in the foreign jurisdiction, with date and place.
Affidavits should avoid conclusory statements unsupported by authority. Courts give weight to analyses that show engagement with primary authority.
Authentication, translation and chain of legalization
An affidavit sworn overseas will usually require authentication before Thai courts will accept it. The practical chain often includes:
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Notarization or sworn before a local authorized officer in the foreign jurisdiction.
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Authentication by the foreign state’s foreign ministry or equivalent (or an apostille where the Hague Convention applies).
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Consular/legalization by the Royal Thai Embassy or Consulate in the country where the affidavit was sworn (if required).
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Final legalization at the Thai Ministry of Foreign Affairs (MFA) or the receiving Thai authority, if requested.
If the affidavit is in a language other than Thai, it must be translated into Thai by a certified translator. The translation should itself be certified and, where the receiving Thai court requires, notarized and legalized through the same chain. Plan the authentication steps early — missed consular stamps or insufficient notarization are common reasons courts refuse documents.
Evidence strategy and attachments
A strong affidavit attaches primary source materials: statutory extracts with section references, full text of cited cases (with translations where necessary), and official explanatory materials. Where factual assertions are made about foreign procedures (e.g., “this office normally issues certificates within X days”), attach documentary proof (official web pages, practice directions, or official letters). Bundling annexes, labelling exhibits clearly and providing a short exhibit index helps judges and clerks review material efficiently.
Practical drafting tips
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Be explicit about jurisdiction: identify which legal system is being opined on (e.g., “the law of the Republic of X (substantive and procedural) as at 1 January 20XX”).
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Limit the scope: answer the precise question set by the Thai proceedings; broad, unfocused opinions are less useful and invite challenge.
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Cite leading authority: include the principal cases and statutory provisions, not just commentary.
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Use neutral language: avoid emotive or advocacy-style language; the affidavit’s strength is its objective analysis.
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Anticipate cross-examination: address obvious counterarguments and explain why alternative authorities do not alter the conclusion.
Costs, timing and typical delays
Obtaining a quality affidavit can take from several days (where an expert is local and the question narrow) to several weeks for complex issues requiring research and translation. Costs vary with the expert’s market rate, time spent, translation, notarization, and legalization fees; cross-border coordination increases cost. Where courts may require the expert to be available for oral examination, budget for potential travel or remote hearing attendance.
Practical courtroom considerations
Thai courts may, at their discretion, require the expert to appear for examination (in person or via video) if the affidavit is contested or the legal issue is central. Agree with the expert in advance on availability and fees for attendance. Also consider whether a local Thai counsel affidavit summarizing procedures for admitting foreign evidence would make the process smoother.
Cross-border enforcement and parallel filings
Where the foreign-law question affects assets or rights in another jurisdiction, consider obtaining comparable evidence in that jurisdiction — a matching sworn opinion under the foreign law or parallel procedural steps to ensure foreign courts or registries will recognize the Thai filing. This dual approach reduces the risk of inconsistent outcomes.
Checklist before filing an affidavit of foreign law in Thailand
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Expert CV and authority to act.
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Clear, written instructions and focused legal questions.
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Annexed primary sources (statutes and cases) with certified translations.
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Notarization and all required consular/embassy legalizations (or apostille where appropriate).
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Certified Thai translation of the affidavit and exhibits (if required).
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Expert availability for potential cross-examination.
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Budgeted fees for legalization, translation and expert attendance.
Conclusion
An affidavit of foreign law is a technical, high-impact piece of evidence in Thai cross-border matters. Its admissibility and persuasive value rest on the expert’s credentials, meticulous citation of primary authorities, correct notarization and legalization, accurate translation, and a focused, reasoned application to the facts. Early planning, expert selection and careful evidentiary preparation greatly reduce the risk of rejection or the need for supplemental proof; where stakes are high, coordinate foreign experts, Thai counsel, and consular steps at the outset to ensure smooth admission and effective use in Thai proceedings.