The attack took place around noon in Narathiwat, one of the country’s southernmost provinces.
A low-level conflict has simmered in Thailand’s south since 2004, killing more than 7,000 people, as rebels in the Muslim-majority region battle for greater autonomy from the state.
Narathiwat governor Sanan Pongaksorn told AFP a suspect had driven a car into police accommodation before abandoning the vehicle.
A bomb exploded shortly after the car was parked, the governor said, adding that police were checking security camera footage to identify the suspect and investigating possible motives.
He said one person was killed and 28 others were injured, including two in critical condition.
The southern region – heavily policed by Thai security forces – is culturally distinct from Buddhist-majority Thailand, which colonised the area bordering Malaysia over a century ago.
In September, a roadside bomb blast killed one police officer and wounded three others.