Kathu Police responded to the scene shortly after 1.30am and found the police vehicle had smashed the front end of a parked Honda City, pushing it into a Toyota pickup truck behind it.
The truck then smashed into the back of a Honda Wave motorbike, which hit a white Toyota Avanza car, which then hit another Honda bike.
The driver of the police vehicle was identified as Pol Lance Corp Tanusorn Jaikaeng, an investigation assitant at Karon Police Station.
Kathu police said the driver had fallen asleep as he passed Patong Hospital, then drove across the road and hit the vehicles. They said the officer would be subject to the legal process.