Shaolin Invincible Guys (1978)

The girlfriend of a con-man is being held in a brothel and he must try to raise 200 tales of gold as a dowry. So he cheats a country simpleton out of his money then goes and loses it in the casino resulting in the country man feeling sorry for him. The two become friends and as they are both expert fighters start working as instructors for a local big boss but this causes real trouble.