Capt Anuwat Nattapong of the Phuket City Police was informed of the accident at 5am.
Officers and rescue workers from the Kusoldharm Foundation arrived at the scene, about 50 metres from the main traffic lights in Koh Kaew, to find a red Honda motorbike on the road with heavy damage to its front.
A white Toyota van parked by the side of the road had suffered minor damage to its rear right.
On the road were two men, as yet unnamed by police, with serious injuries.
Both were rushed to Vachira Phuket Hospital.
The owner and driver of the van, Sanusee Hami, 42, was waiting for the police at the scene.
Mr Sanusee, who lives nearby, told police that he had come home in the van to change his clothes before he picked up a client in the morning. But the motorbike struck his van before he had left.
Mr Sanusee was taken to Phuket City Police Station for further questioning while police continued their investigation, which will include checking CCTV footage from the area, Capt Anuwat said.
Officers have yet to question the two injured men, Capt Anuwat noted in his report.