Officials flew by helicopter on Thursday to examine the Dong Yai national forest reserve and locate areas reported to have been encroached on.
They were led by Maj Gen Sermsak Niyamosoth, commander of the Buri Ram Military District, Yuthachai Pattamasonthi, director of the Nakhon Ratchasima-based Zone 7 Conservation Office, and Somsuan Raksat, chief of the Dong Yai game reserve.
The inspection was in response to reports of villagers having occupied land in the forest reserve, built living quarters and cleared forests for cultivation. More than 500 families were reported to have settled inside the forest reserve in six different groups, illegally occupying altogether 18,800 rai of land.
Authorities are planning to evict them because the forest reserve has been on Unesco World Heritage listing since 2003.
An official accompanying the inspection team said the authorities would first try to persuade the families to move out. If they do not cooperate, they would be forcefully evicted.