When Sakda Vicheansil, a lawmaker from western Thailand, announced his resignation from the ruling Pheu Thai party in early September, his words reflected the extraordinary decline of the country’s most dominant politician, Thaksin Shinawatra.

"Thai people across the country, and especially in my constituency - Kanchanaburi, Constituency 4 - are suffering," he said on Facebook.

"The government has completely failed to resolve their problems."

Former premier Thaksin, 75, has run a populist vote-winning machine in Southeast Asia's second-largest economy for a quarter century but his grip on electoral politics has finally slipped, analysts said.

Outmanoeuvred by a smaller former coalition partner, and with a daughter sacked as prime minister and his once dominant party desperately asking the king to endorse a snap election that it would struggle to win, the billionaire Thaksin is on the ropes.

"For all intents and purposes, the Shinawatra family is politically spent," said Thitinan Pongsudhirak, a political scientist at Bangkok's Chulalongkorn University.

Six premiers, either from the family or backed by it, have been pushed out of power by court decisions or military coups - the latest being Thaksin's daughter Paetongtarn Shinawatra who was dismissed by the Constitutional Court on Friday.

Paetongtarn's exit, stemming from a betrayal by long-time family ally and former Cambodian leader Hun Sen who leaked a call with her in the run-up to a deadly border conflict between the neighbours, has triggered a flurry of deal-making.

Bhumjaithai, a coalition partner that walked out after the leak, said it would form the next government with the support of the parliament's largest grouping, the opposition People's Party.

To counter, Pheu Thai on Thursday announced it would dissolve parliament if its prime ministerial candidate wins a vote scheduled for Friday, leading to a general election.

In either scenario, Thaksin faces a struggle to retain his once-outsized influence, which has won parties backed by him every election since 2001 - until the last one in 2023 when a coalition deal eventually landed his daughter in the prime minister's office.

Paetongtarn's popularity - a proxy for Pheu Thai's standing - has plummeted, from 31.35% of respondents backing her last September to just 9.2% by June, nationwide surveys show.

Thaksin himself faces another legal threat. On Tuesday, the Supreme Court will rule on the legitimacy of his prolonged hospital stay in lieu of prison, following his return to Thailand in 2023, which could potentially result in jail time.

"Pheu Thai is actually losing everything at the moment," said Titipol Phakdeewanich, a political analyst from Ubon Ratchathani University.

"And if next week the court rules against Thaksin, it would be a big disaster for the Shinawatras."

POPULIST JUGGERNAUT

A former policeman with roots in Thailand's north who made billions in the telecoms sector, Thaksin pivoted to politics in the mid-1990s, initially serving as foreign minister and then deputy prime minister.

The Thai Rak Thai party, founded by him, brought Thaksin to power in 2001, when he unleashed big spending on healthcare, rural development and farming subsidies, laying the foundations of his enduring popularity in the agrarian heartland.

His rise also brought him into conflict with the conservative-royalist elite, who saw him as a crony capitalist plundering the economy, creating conditions for a military coup that ousted him in 2006.

Thaksin-backed parties continue to win elections after the coup, while a segment of his supporters formed the "Red Shirt" populist movement that celebrated the former premier, challenging the conservative establishment for almost a decade through street protests and other activism.

From self-exile, Thaksin fronted his sister, Yingluck Shinawatra, who swept the general elections in 2011 and sought to replicate his populist policies. Conservatives closed ranks again to push her out three years later.

It was Thaksin's daughter who took over the mantle in 2023, leading a campaign laden with nostalgia of previous Shinawatra administrations, as her father manoeuvred an unexpected homecoming that analysts posited was made possible with a deal with his conservative rivals.

"This led to many former supporters seeing Thaksin now as a member of the elite," said Suranand Vejjajiva, former secretary-general to the prime minister during Yingluck's term. "Therefore, his base has become smaller."

Once in power, even as Thaksin won a royal amnesty and appeared to exercise backroom influence, Pheu Thai struggled to deliver on its poll promises, including its flagship cash handout programme, which has drawn criticism from its own lawmakers.

"They just rely on a populist platform that is not working anymore in Thai politics," said Titipol.

At least three lawmakers who have broken rank with Pheu Thai in recent weeks underlined its handling of the economy as a key reason.

"The people who elected me had placed their hopes in the government I belonged to," Sakda wrote, listing out lower rice, corn, cassava and beef prices.