But though he lives in self-imposed exile in London, Thaksin remains a dominant figure in Thai politics.
"The poll this Sunday is a continuation of our ongoing political crisis," said Thitinan Pongsudhirak, a political science professor at Bangkok's Chulalongkorn University.
"This election shows the struggle between pro-Thaksin and anti-Thaksin forces."
Analysts say the outcome of the election will be unlikely to resolve divisions between Thaksin's supporters, largely drawn from the rural masses, and those who are against him.
Clear winner unlikely
Al Jazeera's Tony Cheng, reporting from Bangkok, Thailand's capital, said a clear winner will not be seen.
He said: "If a representative of a smaller party becomes the next prime minister, it may create confusion in a country still sharply divided among supporters and opponents of Thaksin Shinawatra."
People's Power Party
The party is led by 72-year-old Samak Sundaravej, six-time cabinet minister under investigation in two corruption cases from his time as governor of Bangkok.
The party is campaigning on a platform of cheap health care, low-interest loans for the poor and greater funds into village-level development.
It has pledged to bring home Thaksin Shinawatra, the exiled former prime minister.
Thailand's oldest party is led by 43-year-old, Oxford-educated Abhisit Vejjajiva, who has been a member of parliament for 16 years.
He has been criticised for not connecting with poor, rural voters.
The party promises free education, a focus on resolving the four-year Muslim insurgency in the country's south and rooting out corruption.
The PPP draws most of its support from farmers, the majority of Thailand's 64 million population, who remember Thaksin's efforts to boost the rural economy.
The party has embraced the populist policies that won Thaksin two landslide victories and plans to bring the toppled prime minister home if it wins a majority in the 480-seat parliament.
"If the PPP doesn't win more than half, Thaksin can't return," Chalerm Yoobamrung, a PPP parliamentary candidate, told more than 10,000 supporters at a rally in Bangkok on Saturday.
In August, a referendum ratified a new, army-backed constitution to replace Thailand's 1997 constitution, widely held to be the most democratic the kingdom had seen.
The new constitution paved the way for Sunday's election, but critics warn the charter will encourage weak coalition governments while returning real authority to the military, the bureaucracy and the royal palace.
General Sonthi Boonyaratglin, the leader of the 2006 coup, has said he will respect the outcome of the election.
The polls are meant to return power from the military to civilian rule, with unofficial results expected by midnight on Sunday.