Mr Cairney, 22, from Stirling, Scotland, was left critically injured after the back of his head hit the road when he fell from the vehicle at about 4:02am, according to police.
Mr Cairney, who holds an undefeated professional boxing record of 10 wins from 10 fights and won the WBO International Welterweight title in Hong Kong last year, was initially taken to Patong Hospital before being transferred to Vachira Phuket Hospital, where he remains under intensive medical care.
Pol Lt Col Surachat Thongyai, the investigating officer handling the case, said Mr Cairney’s condition was considered "50/50" due to the severity of the head trauma.
Police said Mr Cairney had been holidaying in Phuket with relatives and friends from the United Kingdom.
Investigators believe alcohol may have been a factor in the incident. Blood tests have been ordered to determine whether he was intoxicated or had any substances in his system at the time of the fall.
According to the police investigation, Mr Cairney had earlier visited an entertainment venue before attempting to return to his hotel by tuk-tuk.
Officers were told that a dispute arose over the fare when the vehicle arrived at the hotel. A hotel security guard told police that Mr Cairney had attempted to exchange funds using his bank card at the hotel but was unsuccessful and needed to withdraw cash from an ATM. The fare was estimated to be between B300 and B400.
Police believe that after obtaining money, Mr Cairney re-entered the vehicle. However, instead of turning into the hotel entrance, the tuk-tuk continued past the property and accelerated away.
Investigators suspect Mr Cairney was riding in the rear section of the vehicle when he lost his balance and fell onto the roadway.
CCTV footage reviewed by police reportedly shows him falling alone from the back of the vehicle before landing face-up in the middle of the road.
“The vehicle was travelling at speed, but there was no sudden acceleration,” Pol Lt Col Surachat said. “The injured person was positioned near the rear of the vehicle and fell off.”
The footage also showed there were no vehicles immediately behind the tuk-tuk at the time, potentially preventing even more serious injuries.
A woman was reportedly travelling with Mr Cairney earlier in the evening, but police have not determined whether she was still inside the vehicle when the fall occurred. CCTV footage does not show any other passengers at the moment he fell.
Investigators initially considered whether the injuries may have been caused by an assault due to the nature of the wounds. However, after interviewing witnesses and reviewing CCTV recordings, officers concluded that the injuries were consistent with a fall from the moving vehicle.
Police believe the driver would likely have been aware that a passenger had fallen from the vehicle.
“The vehicle should have turned into the hotel to drop off the passenger,” Pol. Lt. Col. Surachat said. “Instead, it continued on without regard for the passenger.”
Officers have identified the vehicle involved through CCTV footage and information recorded by a hotel security guard, including the registration plate number.
The registered owner of the vehicle has reportedly told police that the tuk-tuk had been rented to another driver at the time of the incident. Investigators are now working to identify and locate the person who was operating the vehicle.
Police are seeking statements from both the owner and the driver and may issue a summons if cooperation is not forthcoming.
Pol Lt Col Surachat said that if Mr Cairney’s injuries prove fatal, the driver could face charges of negligent driving causing death, as well as failing to stop and render assistance and failing to report the incident.
Mr Cairney is regarded as one of Scotland’s rising boxing prospects. The Stirling native compiled a perfect 10-0 professional record and captured the WBO International Welterweight title in 2025 after a second-round technical knockout victory. His most recent bout was fought in May this year.
The investigation remains ongoing.