Police arrived at the scene on Thepkasattri Rd and found the tourist, Rodney Wright, 50, suffering from a head injury and a wounded knee, near the truck.
The truck driver, Rakchart Sanpee, 35, told police that he was waiting at the traffic lights when he heard something slam into the back of his truck.
Mr Rakchart said, “I came out and saw an injured man behind my truck, so I called 1669 for help.”
Police took the victim to Thalang hospital after being treated with first aid.