A van taking 25 children to a nursery in Chiang Rai's Wiang Pa Pao district crashed into the rear of a truck, injuring the van driver and 14 children.
The accident on the Chiang Mai-Chiang Rai road in Moo 6 village in Tambon Wiang Ka Long happened at around 7:20am.
The van driver, Kamol Phothi, 59, suffered injuries on his face. A girl on the front passenger seat had her legs stuck in the damaged console and rescuers had to use a tool to free her.
Five of the preschoolers were more seriously injured with two suffering broken arms, one head injury and two others had bruises and cuts.
Everyone was taken to Wiang Pa Pao Hospital and 11 unharmed children were released.
Seksan Wongsuwan, 50, the driver of the six-wheel truck, said he was about to change lane to make a U-turn when the van crashed into his rear.
Police have yet to investigate the accident.