Human Rights Watch on Wednesday urged Thailand's military government to disclose the whereabouts of a prominent rights lawyer who has been missing since his house was raided at the weekend.
Prawet Prapanukul, 57, provided legal assistance to members of Thailand's political opposition group, the United Front for Democracy Against Dictatorship, and served as legal counsel in a high profile royal insult case.
He has been missing since soldiers and officers from the ruling junta raided his house on Saturday, Human Rights Watch said in a statement.
His disappearance comes after Thailand in February shelved legislation to criminalize torture and disappearances after years of working on the bill, prompting concern among rights groups and the United Nations.
"The Thai junta should urgently disclose Prawet's whereabouts and release him if he hasn't been charged with a credible offence," said Brad Adams, Asia director at Human Rights Watch.
"Secretly detaining rights lawyers, critics of the monarchy, and other dissidents has created a climate of fear in Thailand that is generating international outrage."
A spokesman for the junta said he was unable to comment as he did not know about Prawet's case.
Thailand's military seized power from an elected civilian government in a May 2014 coup.
Since then the junta has detained hundreds of politicians, activists, journalists and others accused of being involved in anti-junta protests and activities.
Some have been held incommunicado in unofficial places of detention, such as military camps.
It has also taken a hardline stance against alleged transgressors of Article 112 of the country's criminal code which makes anyone found guilty of insulting the monarchy liable to imprisonment for up to 15 years.
Since 1980, 82 cases of enforced or involuntary disappearance in Thailand were reported to the UN working group on enforced or involuntary disappearances.