The attack occurred at 3:30 am at a concert in a temple fair in Roi Et’s Suvarnabhumi district.
Police believed that a rival gang lobbed the grenade at the teenagers who were dancing on the right side of the stage.
Police found that the bomb was an M67 grenade.
The injured were rushed to the Suvarnabhumi Hospital and Roi Et Hospital. Three of them died at the Roi Et Hospital. They were identified as Wiriwan Sibuala, 40, Sarawut Utla, 16, and Apisit Saengnet, 16.