Capt Natthee Pichitchainitimet of the Wichit Police was notified of the accident at 6am.
At the scene, in the nortbound lanes exiting the tunnel, Capt Natthee and rescue workers found a black Honda Wave on the road, along with Myanmar nationals Kyaw Ye Paing, 23, and Kyawn Ye Naing, 25.
Kyaw Ye Paing, who was driving the motorbike, had suffered critical head injuries and was pronounced dead at Siriroj International Hospital just down the road.
Kyawn Ye Naing was taken to Vachira Phuket Hospital for treatment of his injuries, the seriousness of which were not reported.
Capt Natthee noted in his initial report that he was told by “witnesses” that the “two fell down by themselves” while riding out from the underpass.