There are many different types of land title in Thailand , the majority of which do not allow for the legal right to build on that land. Only 3 land titles are recommended; Nor.Sor.3, Nor.Sor3 Gor, and Chanote.
In the beginning, i.e. the Sukhothai era, most the land in Thailand was in the possession of the people, who reserved the right to individually use said land and to transfer it to their heirs. Later, in the Ayuthaya and Ratanakosin era, the land was owned by the kings. The people had to request a royal grant in order to obtain land. At present, the possession of land has to be in accordance with the principle land administration laws.
BUYING PROPERTY AND LAND
Land Purchase :
Thai law stipulates that a foreigner may not own land in his name, he has the right of ownership of buildings only. If a foreigner wishes to purchase land to build a property he has 2 options;
The land is purchased on 30 year leasehold, with an option to extend the lease for further 30 year periods. Possession of the land is assured by virtue of the fact that the property occupies the land. The lessor cannot seize the property upon expiry of the lease, as the property is separate from the land.
If a foreigner is going to operate a business in Thailand then he may purchase the freehold of the land through his Limited Company. The land will be owned by the Company, not the individual.
Even recent amendments that allow a Thai spouse ( male or female ) of a foreigner to buy land require proof that the money used in the purchase of freehold land is legally solely theirs with no foreign claim to it.
House Purchase :
If however, what you want is a house, the fact that you can't acquire freehold land should not be a deterrent. You may own the building freehold and together with a well constructed leasehold (typically a 30 year lease with two prepaid 30 year renewals )
And a purchase option for the land ( that could be exercised in the event the laws of foreign ownership changed – or you sold the property on to a Thai person or legal entity) you will have effective ownership, yet still remain within the laws of Thailand .