The truck also slammed into the back of Honda car.
The driver of the truck, Kijchan Kijpitak, 49, from Samut Songkhram, told police that brakes on his vehicle failed as he was descending Patong Hill.
Police and rescue workers were quickly at the scene.
The injured have been taken to Patong Hospital. One woman who swerved to avoid the runaway truck sustained serious head njuries after she crashed into a roadside power pole.
Police have yet to release more details about the accident or the survivors.
UPDATE: Medical staff at Patong Hospital have confirmed that Laksameeduen Sawasdeeraksa, 27 – the woman who suffered serious head trauma when she collided with a power pole – died from her injuries this afternoon (July 3).