Lt Chanita Boonyanuwat of the Thalang Police was called to the scene, the northbound lanes of Thepkrasattri Rd about 30 metres south of the PTT petrol station in Baan Lipon, Moo 1, Srisoonthorn, at 12:40pm.
Police arrived with Kusoldharm rescue workers to find the body of Prasong Saejiw, 79, a resident of Cherng Talay, on the road beside his black-white Honda Wave motorbike.
Mr Prasong had suffered fatal injuries to his head and chest, and his legs had suffered severe injury. His body was taken to Thalang Hospital.
The truck and its driver were not at the scene when police arrived, Lt Chanita reported.
A witness at the scene told police that Mr Prasong had rode off from a SuperCheap store at the entrance to the Ua-Athorn government housing estate, heading southbound. He apparently had lost control of his motorbike and crossed the lanes onto the central reservation.
Mr Prasong continued across the central reservation and onto the northbound lanes, where the driver of 18-wheeled truck and trailer, registered in Kanchanaburi, was unable to avoid hitting him.
Lt Chanita confirmed that while she was questioning witnesses, the driver of the truck, Apirom Inthong, had presented himself at Thalang Police Station.
Lt Chanita explained that police will check CCTV footage of the road before determining whether Mr Apirom will face any charges.