He had suffered serious head injuries and was sent to Changi General Hospital in an unconscious state.
The incident took place at the junction of Bedok Reservoir Road and Kaki Bukit Avenue 1 today at about 10.30am.
Photos showed the e-scooter pinned under the bus, while several passers-by attending to the injured rider.
The windshield of the bus was smashed, likely due the impact of the rider crashing into it.
About 90 accidents involving e-scooters and e-bicycles took place in the first half of this year.
The accidents mostly took place on the roads, resulting in 4 deaths and about 90 injuries.