Well, it's the second part of the second Ong-Bak story.
Tien (Tony Jaa) is utterly defeated right away, so a large portion of this movie is basically him training again, and getting better again, and overcoming himself before he can take on his old foes anew. And then, finally, at the very end, he takes on his foes. But not with the same ferocity as he did in the previous.
Overall it just feels like a long sequence of filler that leads up to disappointingly little. After the second movie (where the greatest fighting scenes most definitely are) it all wears down pretty fast. It feels like focus is being placed in unnecessary areas; the story grows unnecessarily complex.
Simpler story: less filler: much better everything.
rated 3/5: not bad