There are growing concerns for the welfare of hundreds of Rohingya migrants on a boat bounced between waters off Thailand, Malaysia and Indonesia that has not been heard from in more than 60 hours.
Around 300 men, women and children were found pleading for help last Thursday on the drifting trawler.
The Thai navy said it had repaired the engine and provided visibly thin passengers with food, water and medicine on both Thursday and Saturday before "escorting" the vessel into international waters.
But the location of the boat is now unknown.
Thai authorities insist the passengers wanted to travel southwards onto Malaysia and say they have had no news of the vessel since around 9pm on Saturday.
Indonesian and Malaysian officials have declined to comment on the status of a vessel which has been subject to what one rights group has coined "maritime ping-pong".
Chris Lewa of The Arakan Project, a Rohingya rights group that monitors boat crossings, said her team were last in contact with the ship by telephone on Saturday evening.
Since then the phones have gone unanswered.
Ms Lewa said: "They had told us that the men were taking all the food and that the women could not get the food. They were only getting little bits left over. That was the last we heard from them."
Tens of thousands of Rohingya, a persecuted Muslim minority in Burma, have fled the country in barely sea-worthy boats across the Bay of Bengal.
Survivors from another vessel that washed up in Indonesia on Friday said at least 100 people had died in fighting between Bangladeshi and Rohingya migrants over meagre rations.
"These boat people have been at sea for weeks and months, without adequate food or any sort of medical care, and they are in a greatly weakened state," said Phil Robertson, deputy Asia director for Human Rights Watch.
Calling on Thailand, Malaysia and Indonesia "to end their cruel game of push backs, and treat these people's lives as if they matter," Mr Robertson said "anything else is just empty talk".
Nearly 3,000 Rohingya and Bangladeshi migrants have swum to the shore or been rescued off Indonesia, Malaysia and Thailand over the past week while others have been turned back to sea in moves triggering international outrage.
In recent years they have been joined by growing numbers of economic migrants from neighbouring Bangladesh looking to escape poverty.
The Philippines said it was ready to help the migrants because it is party to the 1951 United Nations convention on refugees, a foreign affairs department spokesman said.
The spokesman and other government officials did not elaborate on the kind of help the Philippines would give.
Malaysia and Thailand have called on Burma, officially known as Myanmar, to stem the flow of the Rohingya but Burma has refused to take responsibility, claiming the group is composed of illegal immigrants from Bangladesh.
