Phuket police coordinated with Kusoldham first response team at an accident site on the shoulder portion of Thepkrasatri southbound lane, in the area of Moo 1, near the U-turn for Nai Klum village in Thalang's Sisunthon sub district.
The driver of the trailer was named as 32-year-old Tana Daengkrajang of Prachuap Khirikhan, who gave report that the accident occured early in the morning, before 6am.
Tana said he was driving the trailer to deliver steel from Bangkok metropolitan area, and parked, waiting to deliver the steel to an unnamed third party, when he heard a loud noise from behind.
Upon inspecting, he found the 20-year-old Pongsakorn Kongkaew, with a broken leg straddled on the fallen motorbike, and lying back in severe pain in a pool of his own blood surrounding his head.
Mr Pongsakorn was not wearing a helmet and was transported to Thalang Hospital, where is reported to be in critical condition.
His parents told police that he is a Year 1 student at Rajbhat Phuket University, and was on his way to Children's Day activities taking place on campus today.