Rights groups on Tuesday urged Thailand's military rulers to probe allegations a 'Red Shirt' activist was tortured during her near one-month detention by soldiers after the coup.
The army has summoned, detained and warned hundreds of political opponents including Red Shirt supporters of the toppled former government as they smother dissent across the country in the wake of their seizure of power on May 22.
In a video released on YouTube, Kritsuda Khunasen, 27, accused her captors of keeping her blindfolded, tied up and interrogating her under duress between May 27 and June 24.
Human Rights Watch say she told them she was slapped, punched and suffocated during her detention.
The allegations are "further cause for alarm that rights protections are not on the military's agenda," said Brad Adams, HRW's Asia director, urging a swift, independent investigation.
The allegations are a "test case for the junta's respect for human rights," he added.
Thai-based rights group the Cross Cultural Foundation said it was "extremely concerned" by Kritsuda's allegations.
"There should be no secret locations, relatives must be notified and a detainee has the right to meet their relatives and lawyers," it said in a statement over the weekend.
The army, which obfuscated over Kritsuda's whereabouts for several days as concerns mounted for her safety, has denied torture.
Army spokesman Colonel Sunsern Kaewkumner said he met Kritsuda in detention and she was not "tortured or beaten as she says", adding he tried to convince her to "be patriotic and stop conflict" between political rivals.