The latest bomb was hidden around 200 metres from the site of the earlier explosion.
â€œWe believe the bomb had been there since Saturday,â€ said police colonel Chartchai Chanasit, adding that no other explosive devices had been found.
A low-level conflict has simmered in Thailandâ€™s south since 2004, killing more than 7,000 people, as rebels in the Muslim-majority region battle for greater autonomy from the state.
The area, heavily policed by Thai security forces, is culturally distinct from Buddhist-majority Thailand, which took control of the region over a century ago.
The explosions come after one person died and more than two dozen were wounded last month when a car bomb went off outside police accommodation.