The bomb was remotely detonated in Pattani province, targeting monks who were receiving alms during a Buddhist ritual and police officers guarding them, said Col Panya Karawanan, chief of Saiburi police station.
He said a monk and an officer were killed. The wounded included another monk, two police and three civilians.
Pattani is one of three Muslim-majority provinces in predominantly Buddhist Thailand. More than 5,000 people have been killed since an Islamic insurgency began in the region in 2004.
Since the violence started, 19 monks have been killed and 25 wounded in attacks in southern Thailand, according to the regional police operation center.
The insurgents have not issued specific demands but are generally believed to be fighting for an independent Muslim state.