Foreign - Thai owned or marital asset
It is explained in the website of the departments of lands กรมที่ดิน.
Basically it is considered foreign owned as a jointly owned marital assets between husband and wife, and whether registered in the Thai spouse's name or foreigner's name, such condominium acquisition must comply with section 19 of the condominium act governing the purchase of a condominium unit by a foreigner.
This is only different (wholly Thai owned and not subject to section 19 of the condominium act) when the condominium unit is purchased as a personal property of the Thai spouse, separate from marital assets, but then you and/ or your the Thai spouse must follow the same procedure as when purchasing land in Thailand. Then the condo is owned as a separate personal asset of the Thai spouse and considered Thai owned and it will not be part of the marital property owned in common by husband and wife.
The following information comes from the Department of Lands
Normal purchase of the unit
In the case where a Thai national who has a foreigner spouse (whether legitimate or illegitimate) expends money which forms the community property or the jointly acquired property of husband and wife and such is used for the acquisition of the unit, and whether the purchase is made in the sole name of that Thai national or jointly in the name of the foreign spouse as well, the acquisition shall be considered be made by the foreigner. In this instance, the foreigner must be a foreigner within the meaning of section 19:
under 1 foreigners permitted to have residence in the Thailand under the immigration law,
under 2 foreigners permitted to enter into Thailand under the investment promotion law, or
under 5 foreigners or juristic person regarded by law as foreign who have brought in foreign currency into Thailand and exchanged and withdrawn Thai baht from the Thai baht account or foreign currency account), as the case may be.
The Thai national spouse is therefore entitled to purchase a condominium unit in accordance with the entitlement of the foreign spouse and it shall be deemed that such condominium unit us wholly owned by that foreigner because the ownership in a condominium unit is indivisible and governed by section 19 bis.
A unit acquired by gift
In the case where a Thai national who has a foreign spouse, whether legitimate of illegitimate, applies for permission to accept a gift of a condominium unit, such gift being made with the intention that the property will become the community property or such gift resulting in the foreigner having co-ownership therein, the foreign spouse of that Thai national must be a foreigner within the meaning of section 19:
(1) foreigners permitted to have residence in the Thailand under the immigration law or
(2) foreigners permitted to enter into Thailand under the investment promotion law,
and it shall be deemed that the condominium unit is wholly owned by the foreigner and governed by section 19 bis condominium act.
In contrast, a Thai national who has a foreign spouse under section 19 (5) is not allowed to accept a transfer of a gift which is made with the intention that the property will become the community property because the case under section 19(5) is one involving the application by a foreigner for permission to acquire ownership in a condominium unit in a manner of sale, in respect of which payment therefore must be made.
Source: Department of Land