Anti-government demonstrators have vowed to ramp up their calls demanding the resignation of Prime Minister Paetongtarn Shinawatra, while denying accusations that they want a military coup.

The protesters, led by the United Power of the Land to Protect Sovereignty group, made the vow following an unexpectedly large turnout for their rally at the Victory Monument on Saturday.

The rally was held to pressure Ms Paetongtarn to step down over the leaked audio clip of her conversation with Cambodian Senate President Hun Sen.

At the end of the rally, organisers called on demonstrators to regroup at Chamai Maruchet Bridge. 

Apart from the immediate resignation of the prime minister, the group also demanded the withdrawal of all coalition parties from the government.

The group is also opposed to government plans to set up casinos, among other projects. 

Several core leaders have denied calling for a military coup, rejecting accusations made by the Pheu Thai Party and the People's Party.

The group has instead urged supporters to prepare for long demonstrations if no political changes take place by July 1.