Somsak Saengsawang, 26, suffered minor injuries after the bomb exploded under a car in a parking lot outside the
office in Narathiwat province's Sukirin district on Friday, said
police Sub Lieutenant Pokkrong Yodsana.
The bomb was detonated by mobile phone and was believed to have weighed at least 50kg. It destroyed a car and a motorcycle and caused damage within a radius of about 50m, he said.
A short distance away, police found an unexploded 10-kg bomb inside a fire extinguisher near the entry to an outdoor market. They defused the device, which was set to be detonated with an alarm clock, Pokkrong said.
Nearly 800 people have been killed since January last year
in attacks mostly attributed to a revived Islamic insurgency.
Narathiwat, Yala and Pattani are the only provinces with Muslim majorities in the predominantly Buddhist kingdom.
Southern Thai Muslims have long complained of discrimination by the central government.