A boy 'not wearing a seatbelt' died when he was flung from a truck on a flyover and fell 30 feet to the ground.

The six-year-old youngster was travelling with his family when their pick-up truck crashed into the guardrails along the Bang Phli-Suksawat expressway in Samut Prakan province, Thailand on February 19.

He flew from his seat, crashing through the car's windows and plunging from the flyover onto the road below.

Police arrived at the scene and found the pick-up truck damaged with its windows shattered.

Officers believe the boy had not been wearing a seatbelt before the accident. His parents were taken in for questioning.

The driver and child's father, Arthit Chantarasena, 40, said his children were sleeping in the back seat of the car when the steering wheel became stuck. He was unable to control the truck and slammed into the guardrails.

Police Lieutenant Colonel Rungarun Yangyuen from Sam Rong Tai Police Station said officers were interrogating witnesses and gathering footage from surveillance cameras.

Police Colonel Chutrakul Yodmadee, deputy commander of Samut Prakan Police, added: 'We are coordinating forensics and vehicle experts to investigate the case.

'We have ruled out drunk driving since the test results came back negative for alcohol.'

The boy's body was taken to the Central Institute of Forensic Science for a post-mortem examination.