Daze Raper(1995)

Correction Officer Kwok Kam Hung is a gambling addict and owes a large sum of money, so he constantly makes money through the inmates. The department finds out and fires him. Unemployed, Hung seeks other means to survive and recalls a trick formula that will daze the victim and take the victim's money. He first tries and succeeds in dazing a prostitute and taking her money. Hung then decides to inject the daze drug into drinks in convenient stores.