Amazon offers Prime members the Ong Bak Trilogy on Blu-ray / Vudu Digital for $9.99 with free shipping. (Best Buy charges the same. Non-Prime members can spend $49 or more to qualify for free shipping; otherwise, shipping costs $4.98.) That's $1 under our mention from last Black Friday and the lowest total price we could find by $5. It includes Ong Bak: The Thai Warrior, Ong Bak 2, and Ong Bak 3.
Update: It's currently on backorder, but can still be ordered at this price for delivery when available.