I too find his lack of invention a bit worrying. He is not as nimble at interacting with scenery/objects as Jackie Chan now, let alone in his prime, and he has not got the invention or imagination in his choreography either.
What he does have to his credit is the 'one take' massive fight scenes. The 10 minute storming of the restaurant in 'The Warrior', filmed in one uncut free flowing take, was a magnificent achievement, and the climax of Ong Bak 2 seemed to share this strategy, and lasted a shade longer.
The touble is, that if this is all he can build upon/escalate, then the already thin plots are going to suffer, and we will end up with his films being a testament to rehearsals and physical endurance. This will get boring very quickly.
I watched 'Police Story' for about the 1000th time the other day, and it still amazes, even after all this time. I stopped going 'wow' at Ong Bak after the 3rd viewing.