Can foreigners operate 100 percent foreign owned company in  Thailand?
The foreign controlled businesses are currently governed by Foreign Business Act (FBA). The law became into force on March 3, 2000 to replace Alien Business Law which had been effective since November 26, 1972. FBA also specifies which business activities are prohibited to foreign investors and restrict foreign participation in certain business areas. If the activities that foreigners intend to operate are not under restricted businesses, it is possible to establish wholly foreign-owned company for such activities.

There are other possibilities available for foreigners to operate 100 percent foreign owned company in Thailand:

a branch of foreign companies
a promoted company in accordance with either the Investment Promotion Act, the Industrial Estate Authority of Thailand Act, or other laws
a company owned by U.S. citizens by virtue of the Treaty of Amity and Economic Relation
However, a company is required to meet requirements differently on each choice mentioned above.