The government's claim that an anti-monarchist movement aims to overthrow the monarchy may backfire and negatively affect the institution unless the Abhisit Vejjajiva government produces evidence soon to back up the allegation, noted historian and former rector of Thammasat University Charnvit Kasetsiri has warned.

"In a way, this is dangerous for the institution because so many people have been accused and they stand idly to be lynched to death like students during the October 6, 1976 incident," said Charnvit, referring to the October 6, 1976 massacre when dozens of university students were killed in front of Thammasat University by a right-wing mob that believed the students were anti-monarchist.

Charnvit, a leading authority on that tragic episode of Thai history, said the red shirts would almost definitely fight back. "[The charge] is very dangerous to the institution itself. He added that even back in 1976 many of those accused of being anti-monarchist had to hastily be granted amnesty.

Over the past few days, many red-shirt leaders implicated in the alleged plot to overthrow the monarchy institution have begun taking legal action against the government for allegedly libelling them.

Charnvit said the government and the prime minister would be embroiled in lawsuits that could drag on for years.

He said claims that former prime minister Chavalit Yongchaiyudh was part of a conspiracy to overthrow the monarchy made least sense, as Chavalit was a decorated general, a former Army chief and Supreme Commander, who played a crucial role in bringing an end to the communist insurgency in the early 1980s.

"This charge won't work with Chavalit," he said, adding that the whole allegation against some 30 people, mostly red-shirt leaders may "boomerang" against the government. He was "surprised" the government made the allegation in a blatant way, with Abhisit making the accusation publicly, although details were "vague".

"Normally, such allegations are made secretly or with much beating around the bush, so I'm surprised," Charnvit said.

Another surprising aspect was the red-shirt protesters from Bangkok and surrounding areas. Tens of thousands were working class people who join the protest at Rajprasong in the evening who work and reside in and around Bangkok but are originally from upcountry. Charnvit called them "ru-ban" people, a mixture of rural and urban people.

The historian said the current conflict was not limited to Bangkok but had spread to other parts of the Kingdom and the opposing groups were not two elite groups like in the past.

"I don't think the conflict will end in Bangkok," he said.