I saw the 2nd and 3rd Ong Bak movies first, mostly as the setting was more interesting. The first one does seem more like a demo reel than a movie, with Jaa never really seeming in danger of losing. My only other real experience with Thai films is the 2004 monster movie Garuda. It's fascinating, not for the monster (a bird creature in a cave), but the cultural dynamic. There's a half Thai, half French female scientist, and both the Thai characters, and the movie, see her being a half breed as a horrible thing that makes her less of a human (and she seems to see their point). It's also one of the few movies where the military stepping in is the best thing that could have happened, a natural plot point in a country where they actually have official music to be played on the radio every time the Generals step in to take over the government.