The planned anti-government rally at the Royal Plaza on Nov 24 will be the last by the Pitak Siam group, says its leader Gen Boonlert Kaewprasit.
The rally is intended to make the general public aware about the mismanagement of the Yingluck Shinawatra government, said the retired general known as Seh Ai.
Gen Boonlert insisted, however, that there would be no march. He said he would not move the protesters out of the rally site because he did not want to create hardship for Bangkok people.
He claims as many as one million people could turn out but said the rally would not be prolonged. It could end in one day or two days and one night at the maximum.
The first rally staged by Pitak Siam, on Oct 27 at the Royal Turf Club, surprised the government and some other obesrvers by drawing about 20,000 people, far more than expected.
Gen Boonlert has made no secret of his personal desire to see a coup overthrow the Pheu Thai government. However, current military leaders and some of his former colleagues in uniform have tried to distance themselves from such comments.
The timing of the next rally, Gen Boonlert said, had nothing to do with the Nov 25-26 censure debate scheduled in Parliament by the Democrat Party.
The no-confidence debate would not lead to any change in the government as Pheu Thai and its coalition partners have a majority of MPs in the House of Representatives, he added.
A handful of senior figures in the army, alumni from Class 5 and 10 of the Pre-Cadet School, gathered on Friday to protest against the actions of Pitak Siam.
Gen Boonlert pointed out that Gen Chaisit Shinawatra, a leader of the anti-rally group, only held a top position in the army because he is a cousin of fugitive former prime minister Thaksin Shinawatra.
Pitak Siam has levelled three charges against the government: allowing the monarchy to be insulted; being a puppet of Thaksin; and corruption.
Its opposition to corruption has received support from a group called Engineers for the Nation, which says corruption in Thailand has reached a critical level and could ruin the country.
In a statement released on Saturday, it noted that since Transparency International introduced its "corruption perception index" 17 years ago, Thailand has scored poorly, ranging between 2.79 and 3.8 out of ten, with ten being least corrupt.
This showed that past governments had failed to resolve corruption problem, which had grown even worse now, it added.
The group claimed that electronic auctions, which are supposed to make state procurement projects more transparent, had done the opposite in Thailand.
It said research results showed that the e-auction system, initiated by the Thai Rak Thai government, had caused more than 50 billion baht in damage to the country in the past seven years.
It said the government was now trying to revoke strict procurement regulations in order to conveniently spend its fiscal budget by claiming an emergency in settling flood problems as justification.
The 2.2 trillion baht allocated for nationwide construction projects is likely to be spent through the e-auction system, according to the statement signed by Tortrakul Yomnak, the chairman of the group.
Moreover, it said, the government is taking advantage of its parliamentary majority to push through projects without listening to the objections of the people. This is a practice that past governments, even military ones, dared not follow.