Twenty-one passengers were injured, four of them seriously, when a tour bus overturned in Muang district of Maha Sarakham province early on Tuesday, Spring News Online reported.
The accident happened in tambon Kaeng Lerng Chan in Muang district.
The injured passengers were admitted to Maha Sarakham Hospital and Maha Sarakham University's Medical Centre.
Manager Online reported the bus left Mor Chit terminal at 10.30pm on Monday for Mukdahan. It rammed into a roadside tree before overturning. Most of the passengers were sleeping at the time.
Pol Lt Col Sommas Sathittawat, duty officer at Maha Sarakham’s Muang police station, said the accident occurred on a four-lane road.
Police suspect the driver, who is among the injured, fell asleep at the wheel. They will question him later.