That's a hard one as I really like Tony Jaa. I liked all three Ong-Bak movies and also the two 'The Protector'. I can't decide.......
Ong-Bak and The Protector. They're his best-known. There's a great scene in The Protector that's all one take, of him going up a huge spiral atrium taking out dozens of guys. Really impressive. The fights are great; the rest of the movie, not so much. But definitely worth it.
one bak