Writer and director Nicolas Winding Refn directed Vithaya Pansringarm by whispering into his ear: "You are God".
Chang's (Vithaya Pansringarm's) outfit in this movie is what retired cops in Thailand wear.
In his commentary, writer and director Nicolas Winding Refn states that Bangkok is a radically different city depending on the time of day. If it is daytime, it is, in his words, like Disneyland. By night, however, things are far more sinister.
According to a Nicolas Winding Refn Q&A at Bam, the infamous insult "cum dumpster" was added into the movie after Refn (late one night) asked Ryan Gosling to come up with a list of the most vile words you could say to a woman. That word was at the top of his list.