Muang Nong Khai police, paramedics and rescuers went to the accident scene to help the victims.
The driver, Kanchan Tiemkan, 23, was found dead in the seat. Rescuers had to use equipment to widen the seat and pull his body out.
Aniwat Pariwat, 25, was found alive and hospitalised.
Police suspect the driver might have fallen asleep during the drive, as there was no sign of braking on the road when the car crashed into the trees and flipped over.