The driver of the pickup, Amad Hemmawong, 58, panicked after the collision and attempted to drive away towards Phuket Town, dragging Mr Terdpong with him.
Mr Terdpong was dragged under the truck for more than half a kilometre before falling away into the road in front of the Shell gas station in Sapam.
Kusoldharm Foundation volunteers rushed him to Vachira Phuket Hospital but he died in the emergency room from multiple injuries including fractured ribs, a broken leg, haemorrhaging in the lungs and head injuries.
The witness told police that the number plate of the truck had fallen off at the collision site. It was retrieved but police did not have to go looking for Amad; he had already turned himself in.