The blast went off shortly before midnight inside Bannang Sata Indhrachat School where the “Hin Banana” festival is being held. There was a show on the stage at that time.
The explosion slightly wounded Salman Kueji, 14, and Asae Jehteh. Police believe the insurgents hid explosives under a parked pickup.
A witness told police that the pickup had been parked there for a few days before but no one noticed when and how the explosives were planted.
The festival, which started on Thursday continued on Friday and will end on Saturday, after which classes will resume. Bananas are synonymous with the district.