Complex sentence: One of the few professional actors in the movie, Wasir Chou played two characters, the Japanese tourist and Ah-hsian's boy friend, whom the script refers to the "Coast Guard Boy".
Split into simpler sentences: One of the few professional actors in the movie, Wasir Chou played two characters in the movie. The second part he played was as Ah-hsian's boy friend, the script refers to him as the "Coast Guard Boy".