Police and rescue workers were called to the scene, in Soi Nakok, Moo 5, Chalong, at about 8:45am.
The truck was found overturned some 20 metres down the steep roadside slope.
The body of the driver, Deen Jaruek, originally from Tambon Thung Maphrao in Thai Mueang District, Phang Nga province, was found nearby.
Mr Deen had suffered a broken neck.
At this stage police believe the accident was caused by brake failure.
An investigation into the accident is ongoing.