Tony Jaa is the guy in Onk Bak. He hasn't done much in terms of Western movies but was actually as stunt double in the movie Mortal Kombat 2. He is a native Thailand and has done many Martial Arts as a child, including Tae Kwan Do, Muay Thai, and several others. He actually did a lot of additional training just for the movie and doesn't use any wires in it. Based on what I read, his dream has always been to be a great Martial Arts actor and cites his influences as Jackie Chan and Bruce Lee.
Definitely a guy to watch out for. He's got another movie that's suppose to be released in August of this year called Tom Yum Goong: the Game. You may want to be on the lookout for that.
Also, if you like the humor of Jackie Chan, you might like the movie that just came out I think this weekend: Kung Fu Hustle. It's gotten some great reviews so far so might be something for you to check out.