The incident took place in Khao Ang Rue Nai Wildlife Sanctuary, east of Bangkok, and was captured on video from a nearby car.
It is thought that the elephant was hungry and had decided there might be food inside the truck.
Tao, who was driving the car as his wife took the video, said the elephant lumbered across the road as his family was travelling to Chonburi.
"I could not believe that a wild elephant was using its trunk to push the truck over on the roadside," he said.
He added that everyone in his car went into panic as the incident unfolded, especially his son.
Fearing for the safety of the truck driver, he immediately contacted wildlife sanctuary officials.
Officials arrived at the scene and ushered the elephant away. They then helped the truck driver exit the vehicle, he said. The driver escaped his ordeal without injuries.
Tao said he was concerned that the wild elephant could return and attack other vehicles in the area.
"I urge officials to keep a close watch on the area, and motorists to avoid driving near this elephant," he said.
Related stories:
Furious elephant stomps people at ordination ceremony in Buriram
Strolling wild elephants bring traffic to a stop in Khao Yai
100 elephants in Ayutthaya camp may be evacuated as Lopburi River overflows