Two men on a motorcycle hurled two hand grenades at government security personnel manning a checkpoint at a Red Cross Fair in Narathiwat municipality.
The six were injured by the fragmentation of one grenade only, as the other failed to explode.
After the incident, the police detained and questioned one suspect.
Meanwhile, in the adjacent province of Yala, several schools began the first day of the new semester on Monday amid tight security.
Army rangers and defence volunteers provided security at schools in the municipality and guarded the routes on which teachers travelled to school to ensure their safety.
Schools in rural areas are set to reopen on May 16. The Internal Security Operation Command (ISOC) ordered all agencies to step up security measures in line with a plan laid out earlier.