By: Our Correspondent

A mysterious retired general has spread fear through the Thai government, which has invoked the internal Security Act and has clamped down on parts of Bangkok over reports that "violence may be used" by protesters during an upcoming rally to demand an immediate coup.

"If a large number of people are mobilized by incitement, led by those who seek to overthrow an elected government and democratic rule — [action] which is against the Constitution — and there is evidence that violence may be used to achieve those ends, then this is a case of national security," Prime Minister Yingluck Shinawatra told the nation Thursday in a televised broadcast.

The Internal Security Act is to be effective through Nov. 30. Some 17,000 anti-riot police and other security forces were said to be rushing to Bangkok to control the anti-government demonstration, led by retired General Boonlert Kaewprasit, who roused an estimated 10,000 supporters on Oct. 28 in a rally after declaring that "I would love to see a coup, because I know this puppet government is here to rob the country."

The government’s fears apparently have been heightened by reports by security agencies that the protesters would seek to capture Yingluck herself and hold her hostage as well as attempting to raid government premises including the parliament, the prime minister’s Government House offices and the Royal Plaza Hotel where the protest is to be held. The protest will be allowed, but must remain peaceful, authorities said.

Despite Boonlert’s rhetoric, it seems unlikely that the movement will go very far. Yingluck’s Pheu Thai government remains relatively popular with the broad masses, built on a populist agenda that provides considerable social support for the rural constituency outside of Bangkok. She is basking in the support expressed by US President Barack Obama, who met her on Nov. 18 in Bangkok during his trip to Southeast Asia.

And, after the six years of turmoil that ended in violence and the deaths of more than 90 people, most of them protesters, in May 2010 and with the center of Bangkok on fire, there is little stomach for more trouble. The bigger concern seems to be that if major violence erupts, or the rally continues, spreads, and cripples Bangkok, Yingluck may be unable to govern and her administration could tumble, which is why her administration is frightened enough to invoke the ISA.

Boonlert is a new, mysterious figure who is supported by an unknown number of other retired generals, said a senior military officer in an interview, although senior active army figures including the powerful Prayuth Chan-ocha, the current head of the military, oppose any such notion.

Boonlert’s other support appears to be drawn from various right-wing, militaristic organizations including the Dhamma Army, which tries to link devout Buddhism with political confrontation, and has played a role during street protests in the past. The pro-royalist Yellow Shirts, the People’s Alliance for Democracy, may also be seeking an opportunistic role as well. The Yellow Shirts formed the spine of street protest that brought down Yingluck’s brother, Thaksin Shinawatra, in 2006 and was responsible for a major portion of the violence that ensued for the next four years.

Other civilian support for Boonlert reportedly includes elements of the opposition Democrat Party which saw its leader, Abhisit Vejjajiva, suddenly propelled forward after the 2006 coup to become prime minister thanks to Parliament ? but without a nationwide election — in December 2008. Abhisit then refused to allow an immediate election and presided over a nine-week-long crackdown against the anti-coup Red Shirts, who wanted Thaksin reinstalled. The violence left the military’s reputation bloodstained and battered.

Last month, Boonlert announced the creation of a movement named Pitak Siam, or Protecting Siam, to oust the government and protect the monarchy. Siam is Thailand’s pre-1939 name, used when the country was ruled by an absolute monarchy instead of the current, widely revered constitutional monarchy.

Pitak Siam’s peaceful protest on October 28, in Bangkok’s prestigious Royal Turf Club stadium, attracted more than 10,000 people. That protest’s speakers included the National Security Council’s former secretary-general Prasong Soonsiri, and the Armed Forces Supreme Command’s former chief adviser Gen. Pathompong Kesornsuk. A retired air vice-marshal, Vachara Riddhagni, is Pitak Siam’s spokesperson.

More troubling for the government is its inability to determine who else supports Boonlert, how high up and influential that support is, or what other strategy they may have planned. There appears to be no hard evidence to substantiate rumors that the protesters would seek to kidnap Yingluck and hold her, although protests upping the ante and seize government buildings are hardly unheard of.

Boonlert is honorary secretary of the Royal Turf Club, which is under the monarchy’s patronage and was an unusual venue for the October pro-coup rally. Analysts noted that the club’s president is retired Gen. Surayud Chulanont, who did not publicly endorse that rally although he is one of the 19 members of King Bhumibol Adulyadej’s important advisory Privy Council. They retain close and extremely loyal ties to generals and soldiers on active duty.

Although all those diverse groups share a similar aim of ousting Mrs. Yingluck, who Mr. Thaksin described as his "clone", a peaceful rally probably won’t be enough to force her government to collapse, or prompt an immediate coup.

Certainly Yingluck appears to have strengthened her position partly by recently allowing the active military to enjoy greater autonomy to arrange their promotions, lucrative procurement contracts, and other affairs without strict civilian oversight, another senior military officer — who also opposed Boonlert — said in an interview. In turn, the military appears happy to allow Yingluck to rule without being threatened by a coup, even though the two sides remain distrustful of each other.

(Richard S. Ehrlich is a Bangkok-based journalist.)