The attack took place at 10am on the Bacho-Bang Lang Dam Road in Moo 4 village in Tambon Bacho.
Pol Sergeant Wiwat Rakchart, a unit commander of the Bannang Sata police station, died at the scene after shrapnel from the homemade bomb tore through his throat.
The three injured policemen were identified as Pol Lance Corporal Natchapol Prommanee, Pol Corporal Sufree Norapha, and Pol Lt-Corporal Assarawut Rapom.
They were rushed to Yala provincial hospital.
The four were travelling in a pickup truck to deliver a summons order to a suspect in Tambon Bacho.