The movie is set in Thailand with a mix of languages: English, Chinese, Thai, Indonesian. The main plot driver is Tian Xiao Xian (Celina Jade), who intends to donate a very large sum of money to help the police stem the corruption and gang violence in the area. The "bad guys" (the mercenaries being paid to kill Xiao Xian) are led by Collins (Scott Adkins) whose most notable assistance is Devereaux (Michael Jai White). The good guys (the mercenaries who have their own reasons to defend Xiao Xian) are Tony Jaa, Tiger Chen, and Iko Uwais. Of the martial artists, the only one I'm not really familiar with is Tiger Chen. The other four are all pretty much the best available today: Uwais and Jaa in particular I think are outstanding.
The dialogue is actually better than average for a martial arts film, and the whole thing is constructed reasonably well. No one will mistake it for quality drama, but the bar is pretty low when you're watching martial arts movies.
Turns out Michael Bisping - one of the "bad guys" - is in fact a former UFC Champion. The interesting thing here is that practical and/or tournament skills rarely have anything to do with how good you look in a movie, and I thought he looked heavy and sluggish.
When you put Jaa, Uwais, Chen, Adkins, and Jai White all in one movie, the fights should have been better than what we got here. Individually, every single one of them is a really good martial artist. And yet the fights were just ... decent. It felt particularly unjust to watch Iko Uwais losing fight after fight - anyone who's seen the "The Raid: Redemption" and "The Raid 2" knows the man is one of the world's best (screen) martial artists. But ... someone has to lose, and he drew the short straw in this picture.
Fans of the martial arts should probably see this. No one else need bother.