Police and security officers found the body of shop owner Yeeseh Yunu, 61, with bullet wounds to the head and torso after a report of a shooting at 11.20am in Ban Slow in Tambon Rusoh.
Yeeseh was the father of Abdulloh Yunu, who was apprehended last year for questioning over a national security matter and later released.
Police said Yeeseh was sitting in his shop when unknown attackers arrived in a pick-up and one assailant fired an AK-17 machine gun before fleeing. Police suspect the attack is part of ongoing unrest in the deep South.