The martial arts school scene
Anyone who is fairly familiar with martial arts could see an 'error' most others wouldn't think twice about:
He was in Bangkok, but everyone in the school wore gis - most associated with karate or Tae Kwon Do. (from Japan & Korea respectively)
The martial art that would've been most likely featured is Thai kick-boxing. (which *was* featured later in the movie)
* Also, there shouldn't've been any Sumo wrestlers. (different scene) That's a Japanese art.