Lek, a Thai boxing instructor teaches Thai boxing to a group of kids for their self-defence. He is like both teacher and father to the kids Wuth, Catt, Pong and Jib. The four have to look after Wuths little brother, Woon who has a heart problem. Soon, they came across a twist of fate that leads them to fight a gang of hooligans. This causes a sudden heart attack to Woon, resulting him to have a heart transplant immediately. Unfortunately, the hospital they were in has been seized by an international terrorist group led by Paeda. Unavoidably, they get involved and fight against the terrorists, as they need to save Woons life and help their country at the same time.