A little misleading with Tony Jaa on the poster. He plays a prison guard whose trying to get help for his sick child, but his character is not as forefront as you'd expect, but it's all good cause Jaa brings the heat.
Most of Jaa's movies are designed like video games, with Jaa fighting a few random henchmen and then fighting the master of the level (sometimes more like a fighting game where Jaa fights one kung fu master, after the other). In this movie he's more dramatic than action oriented, which is why he keeps the marshal arts real basic.
But basic turns out to be good. Not brushing off what a huge fan I am of Jaa, but there is a certain gimmick he's going for in films like Ong bak as he showcases all he's capable of, but there was something about Jaa just doing the basic kicks and punches that felt more electrifying.
Plus he got to show that he has slightly a little more acting skill than we think (although the love he shows for his daughter is no different than the love he showed for the elephants in the Protector)
As for the rest of the film, it was certainly a well done crime drama. It's a very complex story filmed well and with great action sequences that keep you interested. Good watch.