Some 48 people - passengers and crew - were brought to safety before the rescue operation was suspended late Thursday.
Twenty seven dead as Thai tourist boat capsizes in rough seas
The death toll from the sinking of a tourist boat off Thailand's Phuket island rose to 27 on Friday as rescue efforts continued to locate 29 people still missing.
The Royal Thai Navy said "quite a few bodies" had been found inside the sunken vessel.
The police are investigating the incident, the Phuket Marine Police said, adding the boat was properly registered and was not overloaded at the time of the accident.
It went down about 7-km from the shore and had sunk to a depth of about 38-40 metres, the Royal Thai Marine Corps said in a statement earlier.
Thailand is in the midst of its monsoon season, which begins in May and usually ends in October and often generates high winds and flash storms in coastal areas.
Forty-nine passengers were unaccounted for Friday but believed to have been trapped on the Phoenix as it sank in the Andaman Sea on Thursday afternoon.
Authorities expect the death toll to continue to rise.
Thailand's navy said Friday afternoon that nine bodies of Chinese tourists were being brought to Phuket. Authorities had already confirmed the death of another Chinese man.
Navy official Narong Aurabhakdi said some of the bodies were found by divers who entered the wreck Friday and others were floating in the water.
The vessel, which made a day trip from Phuket despite a weather warning, was carrying 105 people including 93 tourists, 11 crew and tour guide when it toppled in 5-meter-high seas Thursday. The incident sparked a rescue attempt that took place in the dark.
Some 48 people - passengers and crew - were brought to safety 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.
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 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.