The two dead were badly cut by a propeller, Phuketwan has learned. The speedboat crashed when it caught on an anchor rope and flipped over about 200 metres offshore.
There were 29 people on board the speedboat, named Choksuwanni 17. It was returning from an outing to Lan island, seven kilometres off Pattaya.
The boat's ''captain,'' Kengkai Boonsri, 23, is among the injured. It is believed the boat was travelling at speed when it hit the anchor rope.
China's Bangkok Embassy is handling an investigation of the tragic crash, which came at south Pattaya about 1.30pm.
The dead have been named as two men, Dong Feiyue, 30 Mr.Zhang Tao, 29.
Injured are Miss Geng Yanzhi, 33, Miss Xiao Manying, 47, Xiao Xiongping, 62, Qign Xiaolin, 32, Xiao Shungen, 49, Liang Kaiyao,49, and Gu Yu Zhang, 33.
China's Ambassador Guan Mu warned Phuket officials at a public gathering in May that better safety standards have to be applied to protect Chinese tourists. It is believed he carried the same message to authorities in Pattaya.
A total of 2.8 million Chinese tourists visited Thailand last year and one million are expected to visit Phuket alone this year.
Ambassadors from other nations have expressed concern about the manner in which people with little experience or training are allowed to control speedboats on Phuket and in Thailand.
Previous speedboat crashes in Pattaya have killed and maimed tourists.
On Phuket, a Chinese tourist was killed last year and three others were injured when a careless ''captain'' slung a trailing banana boat into the side of an anchored speedboat.
The driver was fined and briefly suspended.