A growing number of expats now own properties in Thailand. Are you one of them and if so, can you confidently say that you own your property legally?
In recent years the market in Thailand has opened up somewhat to foreigners who wish to legitimately own properties. However, there are some grey areas and expats who continue with the structures they put in place some years ago might be in for a shock if they are challenged.
It is illegal for foreigners to own land in Thailand. As an expat you cannot own the land your house stands on. Strata title ownership is allowed. Most apartments and condominiums are strata title leasehold, allowing foreigners to own the units. However, the law caps ownership by non-Thais at 49% of the space in a given development. It thus does not follow that just because you find a leasehold condominium that you can automatically own a unit.

The developer must obtain government approval to have a portion of the units foreign-owned and then there is a strict control over the allocation to ensure that majority Thai ownership is maintained. Developers have been known to be less than honest when it comes to this allocation. They have sometimes allocated space by means that the government disallows, and thus foreigners illegally own their units.
The maximum allowable lease term in Thailand is 30 years, which is considered short in the western world. Leases cannot be legally arranged to run consecutively, removing that option for you to secure a 60-year lease, even though in practice this is often exercised.
If you wish to own a house there is the question of land ownership. Some expats have their Thai spouses own the property. This does not give security to you as the effective owner. Joint ownership is not allowed.
Some systems have been developed for the ownership of land through a Thai company. This is allowable but does not actually give you full proof protection. You are only allowed to own the minority of shares in a local company. Thus you still only have up to 49% ownership of the property in practice. To get around this, arrangements are often made for shares to be held by nominees. Lawyers arrange for a company registration where the legal practice staff are the other Thai shareholders.
via Bangkok Post : Foreign property ownership in Thailand.