The body of a para-military ranger was found in a rice field in Pattani's Khok Pho district on Monday morning, police said.
Pol Lt Col Puvasit Mekhi of Khok Pho police station said the man was later identified as Abdulroman Kaewkamsen, 25, a ranger attached to Rangers Task Force 46.
An autopsy revealed he was hit in the head with a sharp object. He died three to four hours before the body was found.
Police were investigating.