By Agence France-Presse
The Phoenix was carrying 105 people -- mostly Chinese -- when it sank on the way back from a popular snorkeling spot on July 5 off the southern resort island of Phuket.
It was among three vessels which ignored a bad weather warning against island day trips.
The boat's captain, an engineer and the owner of the company that operates the vessel have been arrested and are being held while authorities conduct an investigation, Phuket police told AFP.
Divers and the navy spent more than a week retrieving bodies, some from inside the boat, with the final death toll at 47 Chinese nationals.
Tourists from China made up almost a quarter of Thailand's 35 million visitors last year, official statistics show.
In a statement provided to AFP, the the Ministry of Tourism and Sports revised down its forecasted number of Chinese arrivals for July-December by nearly 670,000, to 5.1 million.
"The factors that caused Chinese tourist numbers to plunge is unsatisfaction over the boat accident which mainly directly affected tour groups," the statement said, adding that August will see a 60 percent decrease in arrivals.
But Thailand is confident that Chinese arrivals will continue rise year on year, the ministry said, adding it expects to welcome more than 11 million Chinese tourists this year.
The disaster was one of the worst boating accidents in recent history in Thailand.
But it received little attention compared to the dramatic rescue of 12 children and their football coach from a cave in northern Thailand, which was occurring around the same time.