With few exceptions, foreigners are generally not permitted outright ownership of land in accordance to the Land Code.  However, the Civil and Commercial Code does allow foreigners other forms of ownership through leases and the Roman law concepts of usufruct or superficies. 
Foreigners can, however, own condominiums, subject to the Condominium Act.
 

Main Sources:  Baker & McKenzie, Chandler and Thong-ek