Do you want to know what is the film's story? Who gives a fiddler's fuck about it! I've seen the first Ong Bak film and I didn't even like it for its serious lack of substance. Nonetheless, I admit that the fight scenes were totally sick.
Here's the description of the story provided by TraileAddict.com in case you really care to see this film:
The legend of Ong Bak 3 begins after Tien (Tony Jaa) has lost his fighting skills and his beloved stepfather at the Garuda's Wing cliff from the raid led by Jom Rachan (Saranyu Wonggrajang). Tien is brought back to life with the help from Pim (Primrata Dechudom) as well as Mhen (Petchai Wongkamlao) and the Kana Khone villagers. Deep into the meditation taught by Phra Bua (Nirutti Sirijanya), Tien finally is able to achieve 'Nathayut'. His talents are put to the test again when his rivals including the Golden-Armored King's Guard (Supakorn 'Tok' Kijusuwan), the mysterious killers in black, and Bhuti Sangkha (Dan Chupong) return for the final massive showdown.