First, the cheesy. The over-arching plot is workable, but a bit simple, in general: a group of young adults get tricked and end up trapped and fighting for their lives. Sounds like a formulaic plot for your average horror film, and, in many ways, it feels like a horror film at times. There's even a hulking, slow, silent strong guy who wears a metal mask and drags an axe around, using it against our "heroes" when he catches up with them. He reminded me quite a bit of Jason from Friday the 13th crossed with Pyramid Head from Silent Hill. There also was the aforementioned armor-plated car, replete with wire mesh-reinforced windshield and a flat black paint-job. In some scenes, this car appears to be the menacing metal death it looks like it should be. In its final scene, however, fighters are fighting each other on and near the car and the martial arts fighters crush the car in with their punches and kicks. The damage wouldn't be this bad on a stock car, must less one plated with metal reinforcement. Cheesy.
The acting is underwhelming, primarily because the actors are stuntmen, but this makes the fight scenes that much better. There is a very annoying character who is obviously comic relief: a traveling musician who was trying to find the wedding at which he's supposed to perform, but ends up performing at a party our heroes are throwing and suffers their fate, as well. He is a short, pudgy flamboyant wimp with a ridiculous short pageboy haircut - sort of an Asian Elton John. He whines a lot and tries to get our heroes to stop and "think" their way through or talk it out... neither of which are really viable options for their current predicament.
The characters that make up the fighting team (which I have and will continue to refer to as "our heroes") and the opposing team of "bad guys" were cast for the movie based on their diverse fighting styles, a choice which led to some really good fight scenes. If you watch the making-of featurette, you learn that everyone did their own stunts and there were a great deal of minor injuries during the making of the film, since the fighters were actually performing martial arts, using real weapons and being lit up with very real fire. This movie probably couldn't have been made in the United States, but evidently, action movies filmed in Thailand don't have to use the level of safety measures as are required in the US. When I see a film with Jackie Chan in it, there are always outtakes showing accidents where Jackie Chan got banged up during the filming. In BKO: Bangkok Knockout, there are similar clips, showing several different actors getting banged up during the filming. It's a film, of course, and there are a few camera tricks here and there where the film is sped up so that moves can be made at a slower pace and then made to look more impressive, but the fights are extremely physical and are much more realistic than, say, wrestling.
When I watched BKO: Bangkok Knockout, I selected English audio and found that I needed the subtitles as well, in some parts. I will warn you that you don't want to use the English audio and subtitles together, unless, of course, it's for comical effect, as they don't say the same thing. J.R. Nip said it's not uncommon for the subtitles to be a more direct translation and the audio to be selected such that it matches the mouth movements better. I can accept this, but there are a couple of places where the two translations are completely different statements, which isn't aided by the fact that the script is a bit laughable to begin with. (Well, unless the Thai version is completely different from both translations.)
If you manage to get over the translation, weak plot, wooden acting and annoying comic-relief character and simply enjoy the extremely realistic (because they're real) martial arts fights for their power and art, you get treated to a beginning - is - the - end - is - the - beginning treatment near the conclusion of the film, which gets interrupted, lest anyone think they were taking any of this seriously, with a campy dance number at the end. This isn't a Bollywood dance number... just sophomoric silliness. Well, at least the actors were entertained.
If you're looking for true cinematic greatness that will become an instant classic or a gripping story, then look elsewhere. If, however, you're in the mood for a nice martial arts action flick with some realistic high-impact fighting, BKO: Bangkok Knockout definitely delivers.