Thai prenuptial agreements and property: what they can and can't protect for a foreign spouse

Can a prenuptial agreement change the property rules of a Thai marriage for a foreign spouse — for example, let them hold an interest in land bought during the marriage? No. Thai law governs any Thailand-situated asset regardless of nationality, and Section 1465 of the Civil and Commercial Code voids any prenup clause that tries to apply foreign law to the marital property regime. What a prenup (สัญญาก่อนสมรส) actually does is narrower and more useful: it puts each spouse's pre-marital assets on the official record as separate property, before the marriage changes the default rules.

What a prenup can lock in

• Pre-marital assets stay separate (sin suan tua). Property owned before marriage, and anything later received by inheritance or as a personal gift, is already separate property by default under the Civil and Commercial Code — a prenup exists mainly to itemise it clearly and put it beyond later dispute, not to create the protection from scratch.
• The "fruits" of separate property can be kept separate too. Rent, dividends and interest earned from a spouse's pre-marital assets would otherwise risk being treated as jointly acquired income during the marriage; a prenup can specify that this income stays separate rather than becoming sin somros.
• Management authority over joint assets (sin somros) — Section 1476 of the Code lets spouses agree how jointly acquired property is managed, on top of the default rules.
• It cannot cover child custody or spousal maintenance, and any provision contrary to public order or good morals is void regardless of what else the agreement says.

A strict, one-time registration window

Section 1466 requires a prenup to be in writing, signed by both spouses and at least two witnesses, and entered in or annexed to the Marriage Register at the district office (Amphur) — at the same time as the marriage registration itself. It cannot be created before the wedding and registered later, and it cannot be registered after the marriage has already taken place; either way, it is void, and the couple falls back to the default statutory regime automatically. In practice this means drafting begins weeks ahead, but the signing happens at the Amphur counter on the wedding day itself, alongside the marriage registration paperwork.

• Changing it later requires a court, not a redraft. Under Section 1467, a registered prenup can only be modified or cancelled after marriage with court authorisation — the court then notifies the district registrar so the change is recorded on the Marriage Register. An informal side agreement between spouses to vary its terms has no legal effect.
• No prenup means the full default regime applies automatically. Property acquired during the marriage becomes sin somros, split 50/50 between the spouses if the marriage ends in divorce — this is the outcome a prenup is used to opt out of for specified assets, not the outcome it creates.

Where this connects to a land purchase during the marriage

It doesn't replace the protection covered in Protecting a foreign spouse's interest when property is bought during a Thai marriage — that guide's registered usufruct and superficies are still the only way a foreign spouse gets an enforceable right in land titled to their Thai spouse. What a prenup adds is upstream of that: if the money funding a future purchase is inherited or pre-marital savings, documenting it as separate property in the prenup builds a cleaner paper trail supporting the Land Office's own sin-suan-tua declaration at the time of purchase — relevant given that Thailand's Supreme Court (Decision No. 14736/2555) treats that declaration as only preliminary evidence, not an absolute shield, if a court later examines where the money actually came from.

For an international couple, a Thai prenup only governs Thailand-situated assets — it doesn't extend to property or accounts held elsewhere, which still need a separate agreement under the relevant home-country law if a couple wants both covered. Independent lawyers for each spouse, rather than one lawyer drafting for both, is the standard and sensible way to keep the agreement enforceable if it's ever tested.