A 3-year-old boy who went missing at a street market was found many hours later in the backseat of a stranger's locked car suffering severe heatstroke and exhaustion, and died shortly afterwards.
Investigators are still baffled how he came to be in the car.
Police Sub-Lt Thongchai Srisamrong, of Tha Kham police station, said the incident was reported to him about midnight on Tuesday.
The boy's grandfather told police the child lived with him at an apartment in Bang Khun Thian district.
Earlier in the day, around noon, he took the child out to buy some fruit and the boy had simply gone missing. The grandfather said he and his neighbours searched everywhere for the boy, but he could not be found.
Later in that night he was told the boy had been found inside a car. He was severely exhausted and suffering from heatstroke. He was rushed to Bang Mod hospital in Bangkok, but doctors were unable to save him.
The car's owner told police the vehicle's door lock had been broken but he had it fixed. He insisted to the police that he had locked all the doors on the car when he left it.
An autopsy will be performed on the boy's body to determine the actual cause of death.
The child's parents and the car's owner will also be further questioned, to determine how the boy got into the car.