The red shirts will issue a warning to forces they believe are attempting to overthrow the government by staging "one of their largest rallies" on June 24.
That day marks the 80th anniversary of the 1932 revolution which brought an end to Thailand's absolute monarchy, ushering in a constitutional monarchy.
The red-shirt United Front for Democracy against Dictatorship (UDD) co-leaders feel they are being pushed back by the ammart (elite) they say are seeking to undermine them via the recent actions of independent organisations.
They are referring to the Constitution Court's order to suspend parliament's reading of the charter amendment bill, the NACC's ruling that Deputy Prime Minister Yongyuth Wichaidit committed malfeasance by certifying the sale of monastic land to a golf course developer, and the Office of the Ombudsman's ruling that the appointment of UDD leader Nattawut Saikuar as deputy agriculture minister was ethically inappropriate.
UDD chairwoman Tida Tawornseth said the ammart networks are active on all fronts against the UDD.
Ms Tida said she had learned anti-UDD elements are infiltrating the red-shirt movement and trying to persuade members to disobey red-shirt leaders.
UDD co-leader Jatuporn Prompan said the situation has now gone beyond the era of judicial activism, in which the judiciary is accused by the UDD of overreaching its authority into the executive and legislative branches.
He said independent organisations such as the Constitution Court, the National Anti-Corruption Commission (NACC) and the Office of the Ombudsman are now acting as if they are "states within the state", which do not respond to the elected leadership.
The public must fight against this trend, Mr Jatuporn said.
He urged the red-shirt members to come together at Democracy Monument on Ratchadamnoen Avenue on June 24 to stage "one of the largest rallies" to drive home a warning against those opposed to democracy.
Mr Jatuporn said the Constitution Court's ruling on the charter amendment bill will affect the red shirts either way.
The UDD had opposed the procedure against the bill from the beginning, Mr Jatuporn said.
Senator Pichet Sunthornpipit, who chairs a Senate committee on parliamentarians' ethics, thought the appointment of Mr Nattawut to the cabinet was not against parliament's code of ethics because all the prosecutions of Mr Nattawut took place before his appointment, although Mr Pichet conceded that he believed the appointment was inappropriate.
However, Democrat spokesman Chavanond Intarakomalyasut yesterday said Mr Nattawut was not suitable for his ministerial post.
Mr Chavanond called on Prime Minister Yingluck Shinawatra to remove Mr Nattawut from the cabinet and said she must not appoint Mr Jatuporn, also a red-shirt co-leader, to the cabinet.
Meanwhile, Pheu Thai spokesman Prompong Nopparit said yesterday the party fully supports its leader Mr Yongyuth retaining the two cabinet positions of deputy prime minister and interior minister.
Mr Prompong was responding to opposition leader Abhisit Vejjajiva's remark that Mr Yongyuth should resign from the cabinet following the NACC's ruling against him on Wednesday.
The NACC ruled that Mr Yongyuth had violated Section 157 of the Criminal Code and committed a serious disciplinary offence by certifying the sale of land belonging to Wat Thammikaram to Alpine Real Estate Co and Alpine Golf & Sports Club Co on March 13, 2002, when he was deputy interior permanent secretary.
The commission clearly said its ruling had no impact on his ministerial posts, meaning Mr Yongyuth can carry on as deputy premier and interior minister, Mr Prompong said.
He said Mr Abhisit was engaging in political game-playing by calling for Mr Yongyuth's resignation.
Mr Abhisit was trying to discredit the government and Ms Yingluck, Mr Prompong said.