Eight officers from Yaha police station’s special operation unit providing protection for teachers were travelling on four motorcycles along the Yaha-Kabang Road in Ban Arsen of tambon Yaha when the explosion occurred late afternoon.
Pol L/C Suchart Yungtinnung was killed at the scene. Two other officers of the same rank, Raewat Yingyuad and Waesa-aree Subaharoh, were wounded and taken to Somdej Phra Yupparaj Hospital.
Pol L/C Waesa-aree succumbed to severe injuries to his head and was pronounced dead at the hospital.
Police said a 20-kilogramme bomb packed in a cooking gas cylinder had been hidden in roadside bush. Investigations into how the device was detonated are under way.
Police suspect Islamic separatists led by Saudi Satapor were behind the attack. Mr Saudi is a key insurgency leader wanted on numerous arrest warrants.
After the incident, a joint police-military force cordoned off a suspect’s house in the local area.