The anti-government rally at the Royal Plaza on Nov 24 will be shut down immediately if any violence takes place, says Pitak Siam leader Boonlert Kaewprasit.
Gen Boonlert made the pledge on Saturday as an economist warned that if the rally is prolonged and turns violent, it could severely hurt the country's economy.
Gen Boonlert, alias Seh Ai, also insisted the rally would not be prolonged and said there would be no seizure of any government offices as some have feared.
The protesters will stay at the rally site and about 1,000 security guards will be on duty to prevent any "third hand" from taking the opportunity to incite violence, he said.
"If the anti-government protest turns violent, it would be immediately called off," said Gen Boonlert.
The red-shirt United Front for Democracy against Dictatorship, which supports the Pheu Thai government, has said that its members would stay away from the Royal Plaza area. Instead, they will gather in Nonthaburi, Samut Prakan and Pathum Thani on Nov 24.
Red-shirt leader Worachai Hema said supporters would stay put in their respective provinces but would be ready to march if any untoward incidents take place.
"We will be ready. If the people's power is seized, we will head to Democracy Monument," said Mr Worachai, a Pheu Thai MP for Samut Prakan.
He said a group of red shirts may also gather at Taksin Monument in Bangkok's Wong Wian Yai area.
Red shirts in Samut Prakan plan a rally on Sunday to voice opposition to Pitak Siam's protest.
Northern red shirts, meanwhile, plan a rally on Nov 24 at the Chiang Mai municipal sport stadium to protest against the "rebel" general who leads Pitak Siam.
Wichit Tamoon, a core leader of the northern group, said members wanted to protect the democratic system and the democratically elected government.
Chiang Mai is the home base of the Shinawatra family and a major area of Pheu Thai Party support.
Red-shirt leader Kwanchai Praipana said supporters in the Northeast would gather on Nov 24 in Udon Thani.
National police chief Adul Saengsingkaew has suggested invoking the Internal Security Act to control the Pitak Siam protesters, but Air Marshal Vachara Riddhagni, a group spokesman, said that would not be necessary.
He said the group's supporters had a constitutional right to gather as long as they were unarmed and did not resort to violence. Pitak Siam group has no thought of inciting violence and therefore the special law is unnecessary, he said.
The armed forces chiefs also believe that existing laws should be sufficient to ensure peace and order.
AM Vachara denied reports that business interests had raised 6 billion baht in funds to be used to topple the Yingluck Shinawatra government. Pol Gen Adul said police had heard the same reports and were investigating.
Meanwhile, various state enterprise labour unions have confirmed that they would also join the Nov 24 anti-government rally. In addition, representatives of students at Ramkhamhaeng and Phra Nakhon Rajabhat universities had told Pitak Siam that they would also turn out, said Air Marshal Vachara.
Thanavath Phonvichai, director of the Economic and Business Forecasting Centre at the University of the Thai Chamber of Commerce, warned on Saturday of dire economic consequences if Thailand is plunged back into political violence.
The tourism sector, he said, would be severely affected and economic growth for 2012 would be lower than 4.5%, compared with 5.5% forecast now.
Mr Thanavath said if the protesters march out from the rally site and violent confrontations with police became protracted for up to three months, tourism related industries wopuld experience millions of baht in famages during the high season.
As a consequence, GDP growth for next year would be less than 4.5%, the economist added.
If there was any change in the government or the Yingluck Shinawatra administration decided to dissolve the House of Representatives, it would affect economic policies and investor confidence, said Mr Thanavath.
As a result, he said, GDP growth next year would be less than 4%.