Answer first
A Thai national married to a foreigner can buy land in Thailand, but since the 1999 Ministry of Interior regulation both spouses must sign a joint declaration at the Land Office confirming the funds are the Thai spouse's separate property (sin suan tua). This means the foreign spouse holds no ownership claim to the land itself, and must protect their position through separate lawful instruments.
What the 1999 regulation actually requires
Before 1999 a marriage to a foreigner effectively disqualified a Thai national from buying land, because any land bought during the marriage was presumed to be marital property (sin somros) in which the foreign spouse held a half interest, which was itself unlawful. The Ministry of Interior regulation of 1999 opened the door again: the Thai spouse may buy, provided both spouses appear at the Land Office and sign a joint declaration that the purchase money is the Thai spouse's separate property alone. The Land Office official records the declaration and only then registers the transfer.
The consequence is legally clean but personally sharp: the foreign spouse has no ownership share, no automatic right of use, and no claim on sale proceeds. The land belongs to the Thai spouse alone.
Sin suan tua vs sin somros
Sin suan tua is separate property: assets a spouse owned before marriage, plus inheritances and personal gifts received during marriage. Sin somros is marital property: assets acquired during the marriage from joint effort or joint funds. The 1999 declaration reclassifies the purchase money as sin suan tua for this transaction, regardless of the actual source. That is the legal fiction that makes the purchase possible, and it is why the Land Office insists on it.
How the foreign spouse can protect their position lawfully
Three registered real rights are commonly used, singly or in combination. A usufruct (Civil and Commercial Code Sections 1417 to 1428) gives the foreign spouse the right to possess and use the land for life or for a fixed term. A superficies (Sections 1410 to 1416) gives the right to own buildings on land owned by another, so the foreign spouse can own the house separately from the land. A registered 30-year lease (Section 540) gives contractual occupation rights with real-right status once registered at the Land Office. All three must be signed on transfer day or shortly after, and registered - not just written into a private agreement. For the wider context see the pillar guide and the Thai property law guide.
Source of funds and the 2025-2026 enforcement climate
Land Offices and the IBAS-led enforcement described in the nominee crackdown guide now scrutinise the source of the purchase money more carefully than before. A joint declaration is not a shield against a nominee finding: if the purchase money in substance came from the foreign spouse and the Thai spouse has no independent means to have provided it, the transaction can be re-examined. The safe route is to keep the paper trail transparent, use the declaration for what it is, and add registered usufruct or superficies rather than trying to disguise the arrangement.
Inheritance and the one-year disposal rule
Under Land Code Section 93 a foreign spouse can inherit land from a Thai spouse by operation of law, but must dispose of the land within one year of acquisition. The house structure can be kept if registered as a separate superficies. In practice most families plan around this: registered usufruct or superficies during the lifetime of the Thai spouse, disposal or transfer within the year after death.