Thailand's navy pulled seven bodies from waters off the coast of the holiday island of Phuket on Friday after a tourist boat went down in heavy seas with dozens of Chinese passengers on board.

The grim find takes the death toll so far to eight, with 49 other passengers unaccounted for but believed to have been trapped on the Phoenix as it sank in the Andaman Sea on Thursday afternoon.

The vessel, which made a day trip from Phuket despite a weather warning, keeled over after it was battered by five-metre (15-foot) high storm waves.

A rescued woman wearing a life jacket hugs a man after a boat capsized off the tourist island of Phuket, Thailand July 5, 2018 in this still image taken from video. Video taken July 5, 2018. Photo: Reuters

"Navy searchers found seven dead (on Friday morning)," Busaya Jaipiem, a spokeswoman for Phuket province told AFP, as helicopters scanned the sea and divers tried to reach the sunken boat.

The Phoenix was carrying 105 passengers, the majority Chinese tourists, when it hit trouble, sparking a rescue attempt that took place in the dark.

Ambulances are seen before recovered bodies of passengers from a capsized tourist boat arrive at Chalong pier in Phuket on July 6, 2018. Photo: AFP

Some 48 people -- passengers and crew -- were rescued before the operation was suspended late Thursday.

But by Friday morning hopes of finding further significant numbers of survivors had dimmed, as ambulances waited to receive the bodies at Chalong Pier on Phuket island.

"I assume they are trapped inside the boat... but I wish some of them have survived," Phuket governor Noraphat Plodthong told reporters.

"I have not yet received any reports of people floating in the sea," he added.

The body of one of the passengers, believed to be a Chinese holidaymaker, had been pulled from the sea late Thursday and brought to shore, shortly before the search was called off for the night.

The Thai navy said the Phoenix had sunk 40 metres below the surface, a few kilometres (miles) off the coast of Koh He, an islet known for its coral formations and popular with day-trippers from Phuket.

"Navy divers, frogmen and marine police divers have already been sent to the scene," Rear Admiral Charoenphon Khumrasee, deputy commander for Thai Navy in the southern region told reporters.

"Helicopters will search for those who may have floated out."

Thailand is already in the global spotlight for a dramatic rescue mission in the north of the country, after 12 boys and their football coach were trapped in a cave complex.

Stunned survivors of the boat accident huddled in blankets on a Phuket pier late Thursday.

Some cried while others appeared dazed as they walked around still wearing their life vests.

"Eleven are injured, of these two are in serious condition," the governor added.

The Phoenix was among several boats that appeared to have ignored a severe weather warning in place since Wednesday to take tourists on day-trips to the islands that dot the seas off Phuket.

A Chinese consular official arrived at the operations centre in Phuket to monitor the rescue effort.

Several other vessels hit trouble late Thursday. Initial reports from officials said all of the passengers on those boats were rescued.

But as details dripped through overnight, governor Noraphat said two passengers were still unaccounted for from another stricken ship.

Phuket is a magnet for overseas visitors including Western sun-seekers and huge numbers of Chinese tourists who make up the bulk of the 35 million people expected to visit Thailand this year.

Thailand has a poor health and safety record and accidents are common on its roads and busy waterways -- especially in tourist areas during the monsoon season which is now biting.