The first body was recovered in early morning of July 6 and 12 more were found just before noon. Forty-three people are still missing.
All boat passengers were Chinese tourists, Thai authority confirmed.
The boat called Phoenix was carrying at least 105 people, including 93 tourists and 12 tour guides, when it was pummelled by huge waves on the way back to Phuket from the popular snorkeling spot of Koh Racha.
The boat was flooded and began to keel over after it was hit by five-metre high waves in the afternoon. Life jackets were later handed out to passengers and inflatable life rafts deployed, said the captain, Somjing Boontham.
Rescuers have saved 51 people. Eleven are injured, two of whom are in serious condition, said Phuket governor Noraphat Plodthing.
Helicopters were dispatched to find those who may have drifted away from the boat while divers were also sent to search inside the sunken boat, he added.
According to the Chinese Consulate General in Songkhla, most of the Chinese tourists are employees of a company who were on a holiday trip with their families to Phuket.
A Chinese consular official has arrived in Phuket to monitor the rescue efforts.
The Phoenix was among several boats that appeared to have ignored a severe weather warning to take tourists on day-trips to islands off Phuket.
Another boat called Senerita also capsized in the same area on July 5 with 39 European and Chinese tourists abroad. All of the passengers were rescued. –VNA