Phuket city police Lt Chalew Taihu was called to the scene to investigate the crash that occurred on southbound of Thepkassattri Rd in Koh Kaew, just 200 metres away from Muslim Wittaya school.
Upon arrival, police and rescue workers found the victim, Kitti Yeemuda, lying unconscious under the wreckage of a Honda Click.
The victim appeared to be suffering from severe head injuries and was taken to Vachira Phuket Hospital.
The truck driver was not at the scene when police arrived.
Witnesses told police that the 18-wheeler truck had been parked on the side of the road since early evening. Just after midnight the motorbike came at a high speed and slammed into the back of the parked truck.
Police are currently looking for the truck driver.
No charges will be filed until police are able to question the truck driver and the victim.