Cambodian police on Friday ruled out a probe into the alleged disappearance of a self-exiled Thai democracy activist after a rights group said he had been abducted in broad daylight from outside his Phnom Penh apartment.

Wanchalearm Satsaksit, a sharp critic of the Thai government led by ex-general Prayut Chan-O-Cha, was dragged into a black car on Thursday evening, according to Human Rights Watch.

Citing several witnesses and CCTV from security cameras, HRW says he was on the phone with a colleague when he was taken by "a group of armed men".

But on Friday, Cambodian police said they knew nothing the of the alleged disappearance.

"We don't know about it, so what should we investigate?" Chhay Kim Khoeun, the spokesman of Cambodian National Police told AFP.

Wanchalearm is wanted in Thailand for allegedly breaching the criminal Computer Crimes Act by running an acerbic anti-government Facebook page.

Since a May 2014 coup, Thailand has vowed to track down pro-democracy critics, especially those accused of attacking the kingdom's unassailable monarchy.

Cambodian police have ruled out a probe into the alleged disappearance of a self-exiled Thai democracy activist in Phnom Penh
Cambodian police have ruled out a probe into the alleged disappearance of a self-exiled Thai democracy activist in Phnom Penh AFP / TANG CHHIN Sothy

Wanchalearm last posted on his personal Facebook account a few hours before his disappearance, writing cryptically "Compromise Mode".

At least eight prominent Thai activists who fled after the last coup to Laos, Cambodia and Vietnam have subsequently disappeared, HRW added.

A spokesman for Cambodia's Interior Ministry suggested the HRW report could be "fake news".

"We don't where HRW got the information," Khieu Sopheak told AFP, adding "there's a lot of fake news out there".

Thailand's government emerged from the 2019 elections but remains a legacy of the coup five years earlier with a cabinet stacked with ex-generals and their military allies.

Pro-democracy parties and activists have been hemmed in by legal cases.

The Prayut government is increasingly unpopular -- more so as the coronavirus rips through the Thai economy.

In an expletive-laden video posted on Facebook June 3 which ran up 12,000 views, Wanchalearm hammered the government and the premier for his "failed administrative skills".