The crash took place at kilometre marker 114 on Highway 32 in tambon Phonangdam-ok, said police, who was alerted at 6.30am on Sunday.
Police and rescue workers rushed to the scene and found an overturned Toyota Yaris car on the road. Three people — two Chinese and one Thai — were safely rescued from the vehicle.
A dead cow, weighing about 150 kg, was found about 50 metres way from the scene. Nobody showed up to claim ownership of the dead animal.
Chatri Sae Jueng, the Thai passenger, told police that he and the two Chinese friends left Bangkok around 5am on Sunday to visit his relatives’ house in Chiang Rai. Their car, driven by one of his Chinese friends, was travelling behind a truck loaded with cows.
When they reached the crash scene, a cow suddenly fell from the truck right in front of them. The Chinese driver failed to change the lane in time, causing the car to slam into the cow before overturning, said Mr Chatri, who was slightly hurt.
The truck driver sped away, leaving his dead animal at the scene. Police are hunting down the driver.