The woman died at a hospital at 5 pm after the accident happened at 12:30 pm.
The injured were rushed to the Nopparat Ratchathani Hospital. They were identified as Patchadaporn Kongkarian, 35, Sampan Wong-anu, 32, Supattra Wong-anu, 9, Woranart Nakhamyaek, 9, Alisa Buarouy, 10, Natthikamol Monjathuras, 11.
Patchadaporn died at the hospital of sustained injuries following an operation.
Pornsri Chanthornkhanma, manager of public relations department of the amusement park, said the accident was caused by a disrupt in the power system of the park.
The power disrupt caused the water pump, which supplied water for the track of Indiana Log ride to stop.
While the water stopped flowing, two boats were struck on the track for about two or three minutes, she said.
Once the water was re-supplied to the track the boat behind was sent by the water to collide into the boat ahead of it, the spokeswoman said.
Patchadaporn's husband, Samphan Wonganu, 33, said he and his family was riding the boat that collided into the one ahead of it.
Samphan, who received slight injuries, said the water stopped shortly after his boat was launched and it fell down the hill and hardly hit into the rear of the first boat.
He said the impact caused his boat to fall out of the track and his wife fell out of the boat. Her head also hit the boat.
Noppakarn Luang-amornlert, deputy manger in charge of administration at the amusement park, said the accident was unprecedented.
"I was shocked to learn about the accident because it has never happened," Noppakarn said.
Wiwat Chamnarmtham, vice president of Siam Park City, said the company would provide compensation for the accident which was the fault on part of the park.