Two horses were found dead on Thursday morning after being struck by vehicles on a highway in Nakhon Pathom, just west of Bangkok.
They had broken out of their stall in a nearby café, leading to two more crashes.
A van and a car hit the horses on Borommaratchachonnani Road at 7.30am. The van was then rear-ended by two other cars. One of the cars hit the van after colliding with a horse.
The owner of the horses said the two animals aged 10 and 11 years had escaped from The Frog Prince Cafe, about 4km west of Phutthamonthon Park on the western outskirts of Bangkok.
They might have broken out because they were frightened by something, she said.
The incident resulted in heavy traffic during the morning rush hour.