Authorities on Wednesday charged eight activists of a civil rights group with violating the military government's ban on public gatherings, after it kicked off a cross-country march on Jan 20 in a rare display of public discontent.
Since military rule began in Thailand in 2014, demonstrations have become a rarity, partly because of orders by the junta banning the public assembly of five or more people.
The eight charged on Wednesday, who belong to the People Go Network of activists and academics, which organised the anti-junta "We Walk" march lasting until Feb 17, have denied the charge.
"We think in the past three years, the junta hasn't been genuine and hasn't listened to the people," said the group's coordinator, Supaporn Malailoy.
"So we march with our friends, with the civil liberties we have."
A pro-democracy protester takes part in a protest against the junta delaying polls in Bangkok, on Sunday. (Reuters photo)
Responding to the comment, National Council for Peace and Order spokesman Col Winthai Suvaree said, "That is just the personal opinion of some people who are already prejudiced."
The eight are to report to a state prosecutor on Feb 26, who will decide whether to take the case to court, the Thai Lawyers for Human Rights group said.
Wednesday's prosecution was an "infringement of fundamental rights and freedoms," 52 civil rights groups said.
"The Royal Thai Police and the government have done some wrongs in violation of these fundamental values, principles and human rights," they said in a joint statement.
"These actions need to be condemned."
The ban on public gatherings was inconsistent with Thailand's international human rights obligations, the International Commission of Jurists said.
"Thailand should immediately end the criminal proceedings," said Kingsley Abbott, its senior international legal adviser.
The 450-km march from Bangkok to the northeastern province of Khon Kaen has drawn participants from civil rights groups concerned about healthcare, alternative farming, natural resources and freedom of expression.
It aims to spotlight growing public frustration with the junta, which has delayed a promised return to democracy, reined in free speech, cracked down on dissent, and pursued projects despite opposition from rights groups and local communities.
Democracy activists were among more than 100 people who gathered on Saturday to protest against the military government and show support for the People Go Network.
The United Nations has also expressed concern over what it calls a deteriorating rights situation in Thailand, including harsh sentences for those convicted of violating the lese-majeste law, as well as other curbs on free expression.