The yacht, Lady D, is believed to have caught fire shortly after 8am, with firefighters called to the marina at 8:20am.
Firefighters at the scene confirmed to The Phuket News that no persons were injured in the fire, but they were unable to bring the blaze under control.
A source told The Phuket News just before midday that superyacht was to be towed out to clear water for safety.
No other yachts in the marina, which was blanketed with smoke this morning, were directly affected by the fire.
The Phuket News was told that the Lady D’s captain and crew are currently all overseas, with one person left to look after the boat.
The incident is being treated as very serious, with Phuket Governor Phakaphong Tavipatana, the Thalang District Chief Adul Chuthong both arriving at the scene to oversee operations.
Police have also confirmed no persons were injured in the fire and have reported that they still have yet to learn what started the blaze.
Thalang Police Chief Col Thirawat Leamsuwan explained that the Lady D had recently returned from Langkawi.
At the time firefighters and police arrived there were no people on board, he said.
Col Thirawat said that the officers had been in contact with the boat’s captain*, Canadian national Ted Blenkers.
“The yacht has about 100,000 litres (sic) of fuel on board. It is being towed out of the marina for safety as the firefighters have not been able to bring the fire under control after three hours,” he said.
* Correction: Not owner, as initially reported. The error is regretted.