When the head of the crime family is killed by a rival family, his son Grant vows to get retribution. As his grief turns into violence, his best friend Ray, a federal agent, does everything he can to keep Grant from going off the deep end.

Continuing from Ong Bak 2's 1440s, Prince Tien fails to revenge his parents' murder by the evil new ruler. The beaten Tien is rescued. Can he bring peace to the kingdom?