Yingluck Shinawatra, the 'puppet' hanging by a thread in Thailand
Thai leader Yingluck Shinawatra is on the brink - but it's the fear that her brother Thaksin is still pulling the strings that is driving the protesters
David Eimer in Bangkok
Mention the name of Yingluck Shinawatra, Thailand's prime minister, to any of the hundreds of anti-government protesters occupying Bangkok's Ministry of Finance and a torrent of abuse follows.
"Yingluck has no brain," said Sunthon Kem, a 69-year-old retired lawyer.
"You can see that from her manner. She's not a real prime minister. She's just a puppet of her brother.''
Sunthon was one of an estimated 1,000 people who stormed the ministry compound on Monday and stayed the night.
It is part of a campaign to force Yingluck and the ruling Puea Thai party from power. About 100,000 people staged an anti-government demonstration in central Bangkok.
But Sunthon's comments are mild compared with the vitriol protesters reserve for Thaksin Shinawatra, Yingluck's older brother. Thaksin, who was prime minister until he was overthrown in a military coup in 2006, fled into exile two years later to avoid corruption charges.
Most Thais believe it is he rather than his sister - the prime minister since August 2011 - who actually runs the country from his homes in London, Dubai and Hong Kong.
"I hate Yingluck, but I hate Thaksin far more," said Wattana, a civil servant from the finance ministry who joined the protesters, but didn't want to divulge her family name. "If Thaksin comes back to Thailand, he'll be dead. I'd kill him myself."
Earlier this month, Puea Thai attempted to push a highly controversial amnesty bill through parliament, which would have pardoned all those involved in political conflicts in recent years.
The move sparked nationwide outrage, with critics claiming it was a licence to allow Thaksin to return from exile.
The possibility of Thaksin's return has plunged the country into a mounting political crisis.
Many are demanding that Yingluck step down and dissolve parliament. They say Puea Thai should no longer run Thailand after it tried last week to change the senate to an all-elected chamber, a move rejected by the courts as unconstitutional.
This week's protests have been the largest since the Thai capital was convulsed by weeks of deadly violence in 2010.
Then, 90 people died and thousands were injured when supporters of Thaksin and Puea Thai, known as "red shirts", clashed with the military and "yellow shirt" supporters of the opposition Democrat Party.
A coalition of anti-government groups has been mounting small-scale protests in Bangkok for months.
Video: Thai political protests paralyse more ministries
But the amnesty bill sparked mass demonstrations and key ministries have now been occupied by hundreds of protesters.
Pitch Pongsawat, a professor of political science at Bangkok's Chulalongkorn University, said: "The amnesty bill was a Pandora's Box that has released all this pressure that has been building up over the last two years since Puea Thai won the election.
"It was a serious miscalculation by Puea Thai and it is Thaksin's mistake. He said last year that the red shirts were like a ship which had sent him so far and maybe he felt he could keep on sailing forever."
Now, the boat has run aground and both Yingluck and Thaksin face their biggest test yet. Parliament will continue grilling Yingluck today, as members consider a no-confidence vote.
"I think Yingluck will survive, but she's in a lonely position," said Pitch. "In a typical democracy, the prime minister is also the leader of the ruling party.
"But Yingluck isn't seen as the true leader because of her brother. She needs to display more leadership."
Already, there are whispers that her older sister, Yaowapa Wongsawat - the member of parliament for Chiang Mai, the Shinawatras' hometown in northern Thailand - is waiting in the wings to take over should Yingluck be forced from office. Yet the protesters' contempt for the Shinawatras is so fierce that dissolving parliament, calling an election and replacing Yingluck with another family member would not be the answer.
"We don't want another election," said Chawalee Rasmaeenin, an apartment block manager. "Since 2001, Thaksin and his allies have profited hugely from corruption. He can use that money to buy votes and win any election."
Populist policies such as the rice-pledging scheme, in which the government buys rice from farmers at above-market prices, further consolidated Puea Thai's popularity in Thailand's densest regions. It is expected that the party would triumph at the polls.
Instead of an election, the protesters talk wildly of running the country themselves through a committee of their leaders.
"This is like a people's revolution now," said Mahussayok Sodee, 47, a businessman. "The people have to run the country. We want real change. We don't want any more politicians."
Such sentiments trigger alarm bells for many in Thailand, which is a country accustomed to unelected governments and military coups.
"I'm afraid that Yingluck stepping down is not the final objective for the protesters occupying the ministries," said Kan Yuenyong, executive director of the Siam Intelligence Unit, a Bangkok-based think tank.
"There's definitely a hidden agenda, one that may lead to some sort of undemocratic means of running the country. The Democrats know they can't compete with Puea Thai in an election. For sure, some of the people behind the protests are the same elite who were involved in the 2006 coup."
That belief is given credence by the emergence of Suthep Thaugsuban, a former Democrat lawmaker, as the protest leader.
So far the Thai military has remained in its barracks. Few police patrol on Bangkok's streets, despite the imposition last night of the Internal Security Act, which allows the government to set curfews, establish checkpoints and seal off roads.
"The government is holding back. It knows that if it imposes a bloody crackdown then the situation will only get worse," said Kan, of Siam Intelligence.
"I think the protesters are trying to provoke the authorities by occupying the ministries and shutting down the government system.
"That's why they occupied the Finance Ministry first. They want to stop the flow of money to the government."
Nor have the red shirts confronted the protesters, although an estimated 50,000 of them are gathered in a sports stadium on Bangkok's outskirts.
There has been silence, too, from Thaksin, the man whose rule left the so-called "Land of Smiles" bitterly divided between the rural poor who support Puea Thai and the traditional elite.
"In the past, I think Thaksin has ignored the hatred his opponents have for him,'' Professor Pitch said.
"But if he really wants to come back, or keep his family in politics, he has to work on more non-confrontational tactics."