In Thailand, the property of a married couple is considered to be marital (communal) property, unless it can be demonstrated that whole or any part of the property is personal property.

A Prenuptial Agreement is a written contract put together by couples prior to marriage which contains a list of personal properties and belongings of each partner, as well as specifications of their rights after the marriage. The purpose of a Prenuptial Agreement is to avoid quarrels and difficulties when it comes to dividing pre-marital property, but in a contested divorce the Court in Thailand has to determine the enforceability of such clauses and compliance with Thai laws.

According to the Thai Civil and Commercial Code, the Prenuptial Agreement is valid when it is entered in a form of the marriage registry or prepared by the spouses in writing, separately from the marriage registry, signed by both spouses, and by at least two witnesses, and entered in the marriage register stating that the Prenuptial Agreement is thereto annexed. The Agreement must be written in the native language of each party.
Both spouses and witnesses must sign in the marriage register. The witnesses can be provided by the marriage registry.

In case the spouse is foreigner, the registrar shall examine the evidence to identify such foreigner (passport, certificate from the Embassy in Thailand) and shall examine the qualification of the foreign spouse (single status certificate) before registering the marriage. Certified translations are required.

Any clause of the Prenuptial Agreement that stipulates that the relations between the spouses and their properties are to be governed by foreign law, is contrary to public order or good morals, shall be void.
After the Prenuptial Agreement is registered, it cannot be modified, except by a Court decision.
Note that a Prenuptial Agreement made in Thailand under Thai law may not always be fully recognized in other countries (and vice versa) or there may be a conflict of laws between the different jurisdictions.