Traffic policeman Second Lieutenant Nguyen Manh Phan ordered bus driver Phung Hong Phuong to pull over his 39-seat passenger coach on Monday after he allegedly refused to show his paperwork, a local police officer said.
When Mr Phung refused and tried to drive off, the officer leapt onto the front of the bus and clung to its windscreen wipers.
Video shot by one of the 2nd Lt Nguyen's colleagues show him struggling to maintain his footing on the bus, which was travelling at 30mph.
He can be heard shouting: "Call the police!" as he dangled precariously from the vehicle.
The driver, who was released in 2010 after serving nearly four years in prison for a fatal traffic accident, eventually pulled over after being chased by police and villagers.