The crash occurred at about 5:35pm on the outbound carriageway of Thepkrasattri Rd, opposite D-Day Metal Power Tool in Moo 1, Mai Khao.
Officers from Tha Chatchai Police Station were alerted to the crash by the Muang Mai branch of the Kusoldharm Phuket Rescue Foundation at 5:45pm. Traffic police and investigators were dispatched to the scene.
Police reported that the collision involved a white Honda Scoopy motorbike, registered in Phatthalung, and a red-and-black Yamaha X-MAX motorbike with a Bangkok licence plate.
Both motorbikes were heavily damaged, lying in the grass beside the road. A concrete roadside kilometre marker post had been broken by the impact.
The Yamaha was ridden by Sarawut Navien, who was carrying three 14-year-old female passengers: Saranya Navien, Thidawan Khaminkaew and Sasiwan Phanomrak.
Rescue workers from the Muang Mai and Mai Khao rescue units provided emergency assistance before transporting all five casualties to Thalang Hospital.
Mr Sarawut and the rider of the Honda Scoopy, whose identity had not been confirmed at the time of reporting, were both pronounced dead at the hospital.
The three girls sustained injuries and remain under medical treatment.
Both motorcycles have been impounded at Tha Chatchai Police Station as part of the investigation.
Police said the cause of the crash remains under investigation, with investigators examining the circumstances before proceeding with any legal action.