More than 90 Rohingya refugees have been found by police in India's Andaman and Nicobar islands.
All of them were starving and seriously dehydrated, police said; 25 have been admitted to hospital.
The refugees told police they had been set adrift with little food and water in a boat without an engine by the Thai navy. Thailand has denied the charge.
Thousands of Rohingyas - a Muslim minority group in Burma - have fled to the country to escape persecution.
An estimated 200,000 Rohingyas live in refugee camps in Bangladesh. Many of them - especially those living in unofficial camps - attempt to escape poor conditions by attempting to get to south-east Asia by sea.
"We found them in villages in the Car Nicobar islands, where they were desperately searching for food and water," police officer George Lalu told the BBC in a telephone interview from the Andaman and Nicobar islands.
The Rohingyas said they were trying to enter Malaysia illegally through Thailand with the help of "agents" before they were caught by the Thai navy, he said.
Doctors at the hospital told the BBC they had been at sea without food and water for more than a week.
In a statement recorded by the police in Car Nicobar, one of the refugees said they were kept in a dark room with minimum food for about a week.
After that, they said, they were set adrift in open sea in an engine-less boat with minimal rations and water.
"They say more of their people may be on the high seas, drifting around in boats without engines and with no food or water," said Mr Lalu.
Thai authorities have denied that they have forced any of the Rohingyas onto the high sea in engine-less boats.
They said they had "intercepted" a group of 91 Rohingyas in Songkhla province in early January.
"But we deported them after proper formalities," said a Thai official in Songkhla.
In December 2008, nearly 300 Rohingyas were rescued from the Andaman Sea after their boats were towed to the high seas by the Thai navy and their engines removed.