Before Dawn (1984)

Mok Ka Bo is a young lad with a few problems. He's just cut loose from a relationship with Fung, a violent lad who can't accept being dumped and wants him back. Ka Bo takes after pretty schoolgirl Margaret, who is apparently a top student and quite respectable, but has a poor and unhappy home life. Ka Bo also has a difficult relationship with his mum, a middle-aged hooker whose use-by date has arrived.