He was identified as Pol Sub-Lt Phana Sricharoen, 61, a former deputy investigator chief at Muang Pattani police station.
Pol Maj Gen Phot Suaysuwan, chief of Pattani police, said the shooting occurred at 8.10pm on the Pattani-Nong Chik road at Ban Don Rak in Nong Chik.
According to witnesses, Pol Sub-Lt Phana was travelling back home on his motorcycle when a gunman riding pillion on another motorcycle fired on him with a handgun.
The former police officer was shot in the back and head and died on the spot.
The assailants stole Pol Sub-Lt Phana’s handgun before fleeing.
Police blamed separatist militants.