It is believed to be the body of an Egyptian man, aged 24, who disappeared into the water near Baan Songprag in Phang Nga, the province north of Phuket.
The body of another tourist, a 28-year-old man from Kuwait, was recovered on the same day.
Two other tourists in the raft, a 24-year-old woman from Egypt and a Kuwaiti man, aged 48, were rescued, treated in a local hospital and allowed to return to Phuket.
It is believed most of the six whitewater raft companies that operate on the river had decided not to work on the day of the tragedy.
Severe monsoon weather over the Phuket region had dumped large amounts of rain, swelling the steams and making rafting unsafe.
The body of the man was found about 8.30am and police were hoping to be able to reach the scene about 10am.