Pol Maj Udon Yana, a police officer of Mueang Lamphun police station, said the accident happened at about 34 minutes after midnight on the Chiang Mai-Lampang superhighway.
Udon said the truck was apparently speeding and hit a road sign and overturned and slipped into the two-metre ditch. The driver and five passengers were found by rescuers to be underwater.
The driver was identified as Sanguan Puansing, 33 and the passengers as Natthapong Wongnetnapha, 24, Jakkrit Niamtha, 24, Jessada Puansing, 23, Thirapat Kanthiya, 23, and Nattapong Wisapa, 22. All were residents of Lamphun’s Pasang district.
The bodies were sent for autopsy to determine whether they drowned or were killed by the crash’s impact.