"When the day comes, we will seize the ruling power immediately based on the constitutional provision that the sovereign power belongs to the Thai people," said Suthep Thaugsuban, secretary of the People's Democratic Reforms Committee (PDRC) after meeting with his allies.
This will depend on either of the two scenarios - when anti-graft body National Anti-Corruption Commission charged Yingluck with dereliction of duty in the controversial rice pledging scheme or the Constitutional court rules to impeach her for transferring National Security Council chief Thawil Pliensri, he said.
Suthep's call came as about 1,00,000 pro-government activists are expected to mass on the edge of Bangkok in a show of support for Yingluck, who is facing mounting legal cases that could see her removed from office.
Earlier, "Red Shirts" or the United Front for Democracy Against Dictatorship - as the group is formally known, had said 5,00,000 supporters would enter the city.
More From This Section
"Red Shirt" leader Jatuporn Phompan said they were not looking for a confrontation with anti-government protesters and that their presence is to show strength and support for Yingluck.
Suthep, a former deputy Prime Minister, said with the removal of Yingluck, power would return to the people. "That'll be the day we can appropriately announce ourselves the sovereign because the power now returns to the people."
"We won't allow them to go abroad. We will appoint the prime minister of the people and submit the name to the King countersigned by him. After that, we'll set up the People's Council, which will lead reform before the country can proceed with a fresh election," Suthep said.
The anti-government protesters have occupied Bangkok's sprawling Lumpuni park near the financial district for weeks now.
The protesters, mainly urban and middle class Thais, want the Yingluck government to make way for an unelected "people's council" before a new round of elections are held.