Engineer K. S. Ng, 47, didn't realise he was being pickpocketed on his bus ride to work.
He later found his trouser pocket and wallet slit and $100 in cash missing.
So he stayed on the bus to go home and the same two men who were with him earlier boarded the bus.
The bus driver locked the door to prevent them from escaping. But the plump man who sat next to Mr Ng earlier slammed himself against the door, forcing it to open and fled.
His companion also escaped.