Property is purchased during the marriage is not and will not be jointly owned.
Property Ownership in Thailand
Foreigners are not allowed to co-own land in Thailand even with their spouse. If a Thai national is married to a foreign national, the land department will not allow the Thai national to register the property without evidence that the land was purchased by the Thai national with personal assets. This is usually in the form of a joint declaration between the foreign national and the Thai spouse. The declaration states that the Thai spouse purchase the land with their own personal funds.
The result of the statement is that the foreign spouse has no claim to the property. The Thai spouse has the right to sell, mortgage, transfer, or exchange the property without the consent of the foreign national. Real property (land) can never become marital property and will always be the separate property of the Thai spouse. However, property on top of the real estate such as a house can be jointly owned by a foreign national and a Thai spouse.
Other Issues about Property Ownership for Foreigners
There are also issues if a foreign national wants to purchase a condo unit in Thailand. A condominium development can sell units to foreign nationals as long as the foreign ownership does not exceed 49% of the total condominium development. If a condo unit is purchased by a Thai national married to a foreign national, the condo unit is considered to be foreign-owned. If the married couple issues a joint statement that the Thai spouse used their separate property funds to purchase the condominium unit, the condominium unit will be considered Thai owned.
The problem with purchasing real estate through a Thai spouse is that in the event of a divorce, the real estate may be considered a property of the Thai spouse. If the foreign national attempts to state that the money that was used to purchase the real estate was from their separate property, the foreign national risks criminal charges for filing false statements with a government official.
The better way to owned a land or property even after you have married a Thai person is to owned it under a Thai Limited Company. This way, you can transfer the ownership of the property by transferring the ownership or command of the company. For more information about using a Thai company to own a property in Thailand, read this article
