The 92 Rohingya waded ashore on the Thai mainland north of Phuket on Thursday and were last seen being trucked to an unknown destination. Locals were told the men and boys were headed for an Army base.
The deputy Asia director of Human Rights Watch, Phil Roberson, said yesterday evening: ''We are concerned by these reports and we would like the Government to clearly explain where these people are and what they plan to do with them.''
It was a ''worrisome development'' to have the detention of illegal arrivals in Thailand once again removed from the Immigration authorities who usually handle such matters, he said.
Fresh questions about Thailand's policy towards the Rohingya boatpeople are being raised as US Secretary of State Hillary Clinton prepares for a history-making visit to Burma, where the Muslim minority is deprived of citizenship and driven to pay people traffickers to escape by sea.
While the Burmese government wants to chair the Association of Southeast Asian Nations in 2014 and has recently shown limited but encouraging signs of reform, its most repugnant policy, under which the Rohingya are denied every basic human right, remains in place.
Burma's denial of Rohingya rights leaves the whole region without a hope of resolving the Rohingya boatpeople issue. Thousands are expected to put to sea between now and April, aiming for neighboring countries, to try to flee Burma's repression.
In 2008-2009, after almost 5000 boatpeople arrived in a single ''sailing season'', Thailand took the covert and drastic measure of towing unwanted Rohingya out to sea and cutting them adrift.
Hundreds drowned before survivors arrived in Indonesia and India's Andaman and Nicobar islands, as Phuketwan and the South China Morning Post newspaper in Hong Kong were the first to reveal.
The concern of Human Rights Watch and other international bodies is that the disappearance of the latest batch of unwanted arrivals is a ghastly reminder of that tragic failed policy.
''Thailand needs to produce these people,'' Mr Robertson said. ''Trucking them off into the distance is no answer to this problem.''
There was a whole list of questions about the unexplained detention of the group that needed to be answered to ensure Thailand was meeting its human rights obligations, he said.
The absence of information from the Thai Government was cause for ''very serious concern.''
The latest Rohingya arrivals scuttled their rickety vessel on Thursday and waded ashore near the port of Kuraburi, in Phang Nga province, north of the international holiday island of Phuket.
Local authorities were told the men and boys would be handed to the Army, which has a base in the province of Ranong, further north on the border with Burma.
It was on a small, uninhabited island off the coast near the Army base that Rohingya were first secretly detained in 2009, then towed out to sea and cut adrift.
After that reprehensible treatment was revealed, boatloads were again handed over in the conventional manner to Thai Immigration officials. Immigration detained groups who landed on Phuket and south of Phuket earlier this year.
Because the Rohingya do not have citizenship, they cannot be officially returned to Burma. It is believed groups apprehended in Thailand earlier this year have been surreptitiously returned to the people traffickers.