It exists for the time being as only a title and brief synopsis on the project board outside Sahamongkol Film's offices at the American Film Market - key art and casting will have to wait until the formal announcement some time down the road - but we now know what is next for Ong Bak director Prachya Pinkaew.  Titled Ta Bang Marn the film is slated for a 2010 release.  Here's the synopsis:

The new epic martial arts action adventure set in a land long forgotten in the Southeast Asian history.  Prachya Pinkaew is back to direct his most ambitious project to date about a group of village girls who team up to protect the "special child" that will change the destiny of the region against all harm.