A Thai cabinet minister who emerged from hiding on Tuesday to make the first public appearance by any member of the ousted government since a military coup last week was detained by soldiers after he urged a return to civilian rule.

About half a dozen soldiers took education minister Chaturon Chaisang into custody in a chaotic scene at the Foreign Correspondents' Club of Thailand, where he had just finished giving a surprise news conference.

The junta, which seized power on Thursday, is already holding most top members of the south-east Asian country's elected administration and has ordered the rest to surrender.

Chaturon called for elections and warned that resistance to the army overthrow could grow, which could lead to "a disaster for this country".

When the news conference was finished and Chaturon was being interviewed by Thai journalists, soldiers entered the room, surrounded him and escorted him out through a crowd of reporters.

Before being hustled into an elevator, Chaturon said: "I'm not afraid. If I was afraid, I wouldn't be here."

The military takeover, Thailand's second in eight years, deposed an elected government that had insisted for months that the country's fragile democracy was under attack from protesters, the courts and the army.

The country is deeply split between an elite establishment in Bangkok that cannot win elections and a poorer majority centred in the north that has begun to realise political and economic power.

Before his detention Chaturon said a "coup d'etat is not a solution to the problems or conflicts in Thai society, but will make the conflicts even worse".

He said he had told only a few people in advance of his appearance. He said he would not resist arrest or go underground, but since he did not "accept the coup, I could not report to those who staged it".

"I still insist to use my own rights and liberty to call for returning the country to democracy," he said.

After declaring martial law on 20 May, General Prayuth Chan-ocha invited political rivals and cabinet ministers for two days of peace talks to resolve the crisis. But those talks lasted just four hours. At the end of the meeting, Prayuth ordered everyone inside to be detained, and announced the army was seizing power on state television.

Prayuth, who was endorsed on Monday by the king as the country's new ruler, warned opponents not to criticise or protest, saying Thailand could revert to the "old days" of turmoil and street violence if they did.

Still, small numbers of protesters have gathered on Bangkok streets in defiance of martial law. Several hundred people gathered on Monday at Victory Monument and eventually dispersed on their own, vowing to return on Tuesday.

The junta has ordered more than 200 people to report to the authorities. Among them are scholars, journalists and political activists seen as critical of the regime.

It is unclear how many are in custody, but some have been released, including former prime minister Yingluck Shinawatra, who had already been forced from power by a court ruling before the coup took place