Thai soldiers scuffle with anti coup protesters during a planned gathering in Bangkok on Sunday. Thailand's military junta said it had disbanded the Senate and placed all law-making authority in the hands of the army chief. Photo: AFP

Former Thai Prime Minister Yingluck Shinawatra has been released from military custody as of Sunday, CNN quoted a highly placed source in the junta as saying.

The military has detained Yingluck and scores of other ousted government leaders and political figures since the coup, which brought sharp international criticism.

"I ask for people's understanding on the current situation and that they refrain from anti-coup rallies, because democracy cannot proceed normally at the moment," said junta spokesman Colonel Winthai Suvaree Sunday morning, adding a warning against using social media to "incite" unrest.

Public anger at the Thai military's coup grew Sunday as more than 1,000 protesters shouting "Get Out!" marched across the capital Bangkok in defiance of an army warning against protests.

Demonstrators began marching in the Chidlom district and made their way across the city to the Victory Monument cheered by onlookers, an AFP reporter at the scene said, after a tense standoff with armed soldiers in the city's retail heart.

It was the largest expression of dissent since the army seized power on Thursday after months of political turmoil.

There was no sign of soldiers or police on the streets during the march Sunday, which went ahead despite a junta statement calling on people not to protest and a martial law ban on gatherings of more than five people.

"I am not afraid of them because the more we are afraid of them, the more they will stamp on us," protester Kongjit Paennoy, 50, told AFP. "We want an election - to choose our own boss."

Before the main march, minor scuffles broke out as dozens of protesters staged a boisterous demonstration, jeering angrily and pushing at lines of armed soldiers outside a Bangkok shopping mall.