According the Video ETA.... September.

http://videoeta.com/movie.html?via=form&id=71199

Ong-Bak: The Thai Warrior

In Theaters: February 11, 2005
On Video: Estimated for September 2005
Starring: Tony Jaa
Petchthai Wongkamlao
Pumwaree Yodkamol
Director: Prachya Pinkaew
Genre: Action
Synopsis:
Rating: R for sequences of strong violence, language, some drug use and sexuality
Length: 107 Minutes
Box Office: $4.5 Million
Studio: Magnolia