A bus and a truck collided in Phrae province on Tuesday morning, injuring 45 people.
The Highways Department said the collision occurred about 6.15am on highway 103. The bus ended up overturned on the side of the road.
There were no details given about the truck and its occupants, who were said to be uninjured.
The bus was carrying 47 passengers and crew. It left Bangkok on Monday night for Chiang Saen district in Chiang Rai province.
Officials said that 45 people on the bus were injured, one of them seriously.
The cause of the accident was being investigated, police said.