Sirichai Suksaaran, police lieutenant of Bannang Satar, said: "The insurgents target Buddhists in an attempt to scare them away from their villages."
More than 200 Buddhists from two villages in Yala evacuated their villages last month.
Suspected fighters ambushed and killed two policemen who were patrolling Yarang district and Pattani province.
In Narathiwat province, two men entered a shop and shot the owner at close range.
They were believed to be separatists, police said, because they did not take any money from the victim.
Also in Yala, in the Krong Pinang district, a bomb concealed in a fire extinguisher and buried by the roadside killed a soldier as his patrol drove by in a Humvee. Two other soldiers in the vehicle were injured in the incident.