Thai company with a majority Thai shareholding (in number of shareholders and percentage of shares) is through normal shares with voting rights - the only vehicle available for foreigners to have their investment in land in Thailand.
A lease in Thailand can be registered in the Land Department for a period not exceeding 30 years, and when the fixed registered term runs out the lease comes automatically to an end. These contracts between the land owning company and the leasehold buyer can be complex and must at least separate ownership of the house from the land and often include additional 30-year lease terms and the option in the contract (or addendum to the contract) to transfer the land to a freehold title.
Foreigners can’t own land as a private individual but are allowed to own the building separate from the land. Basically there are 2 ways of obtaining ownership over the house separate from the land (which you may own/control through an SPV),
a.) you build a house upon leased land or
b.) you buy an existing house separate from the land and obtain a land lease. Transfer of an existing house must be in writing and registered with the competent authority (i.e. the Land Department/ branch office). The transfer of ownership of an existing house starts at the local land office and requires a 30 day public announcement of the sale at specified locations after which the transfer of ownership of the house is completed by the local land office.