The bounty was announced by Pol Lt Gen Korkiat Wongworachart, assistant national police chief.
He said investigators found images of four people suspected of planting the bombs at two locations, a 7-Eleven convenience store on Polpichai Road and the car park at Hat Yai police station on Tuesday.
He said the suspects’ behaviour in each case was similar. One person parked a vehicle at the bomb scene, and was later picked up by a motorcyclist.
The police believed the two bombs were planted by the same group that planted bombs at three locations in Sadao district of Songkhla late last year.
Police obtained arrest warrants for two suspects in the Sadao case and one, Abdulloh Deng, was arrested.
Bomb victims who have been discharged from hospital already received 10,000 baht each in government compensation and those who remain in the hospital will receive 25,000 baht each.
Ten people were reported injured in the two explosions on Tuesday.