The driver of the vehicle was identified as Anusorn Junhroonruang, police said. Mr Anusorn had been hired by parents of seven kindergarteners living in his Cha-uat district neighbourhood to take their children to and from school using his pickup with extra-large cab.
Mr Anusorn told police he picked up seven children, including the four-year-old, this morning from their homes and dropped them at their schools as usual. He then parked the pickup at Cha-uat police station and, without realizing that the boy was still sleeping in the back seat, took a motorcycle to run errands elsewhere.
It was not until about noon when he started wondering if he had dropped off the four-year-old boy at school. He rushed to the vehicle and found the boy locked inside, and already dead.
The driver then called police and the child's parents to tell about the incident, regrettably admitting that he had forgotten the young child in the vehicle, causing his death.
Pol Lt Praponsak Paereepas, a district police investigator, said the child was likely to have died at least three hours before the driver returned to his vehicle.
Mr Anusorn was charged with recklessness causing death, Pol Lt Praponsak said.