Thailand’s ex-prime minister Thaksin Shinawatra entered prison to begin serving an eight-year sentence on Tuesday, hours after returning to the country following years of self-imposed exile.

The divisive former leader returned on the day that a party affiliated with him faces a key vote on its path to form a new government.

Mr Thaksin has said his decision to return has nothing to do with the Pheu Thai party’s bid for power, but many believe the party made deals with pro-military parties to facilitate his return.

The 74-year-old billionaire flew from Singapore in his private jet and landed at Don Mueang International Airport in Bangkok at around 9am local time.

Thai broadcasters aired live footage of him walking out of the airport’s private jet terminal with his three children, including his youngest daughter, key Pheu Thai member Paetongtarn Shinawatra. His grandchildren were also seen.

As he left, Mr Thaksin placed a flower wreath and bowed in front of a portrait of Thailand’s king and queen at the gate of the terminal. He spent a moment greeting supporters and the media waiting in front of the terminal but did not speak.

Hundreds of his supporters had gathered outside the airport hours ahead of his arrival, donning red, a colour long associated with Mr Thaksin, and holding sign with welcoming messages. They showed their devotion to him with songs and chants, then raised raucous cheers when he appeared at the entrance.

Makawan Payakkae, a 43-year-old from Maha Sarakham province, said: “I feel fulfilled that I travelled here today to pick him up. If possible I want to hug him. Everyone has tears, tears coming out of their eyes.”

Mr Thaksin promoted populist policies and used his telecommunications fortune to build his own Thai Rak Thai party and be elected prime minister in 2001. He was easily re-elected in 2005, before being ousted in a military coup in 2006 and fleeing into exile a few years later.

Paetongtarn posted family photos with her father in the middle on Facebook with a message thanking people who went to the airport to welcome him, saying: “Me and my family are very grateful.”

Mr Thaksin’s convoy first went to the Supreme Court, which confirmed a criminal conviction and sentence given to him in absentia during his exile. He then left the court and went to Bangkok’s main prison.

Mr Thaksin was convicted after he fled of several criminal charges which he claimed were politically motivated.

Pheu Thai is the latest in a string of parties affiliated with Mr Thaksin. The military coup that ousted him triggered years of upheaval and division which pitted a mostly poor, rural majority in the north that supports him against royalists, the military and their urban backers.

Less than a week before May elections, Mr Thaksin announced he would like to return before his birthday in July, but the plan was repeatedly delayed, with him and Paetongtarn citing both post-election uncertainties and his health.

Pheu Thai came second in the elections but took over leadership in forming a new government after the surprise winner, the progressive Move Forward party, was repeatedly rejected by conservative senators appointed by a previous military government.

Move Forward’s reform agenda appealed deeply to many Thais, particularly younger voters who were disenchanted by nearly a decade of military-backed rule, but was seen as a threat by the country’s conservative elites.

After more than three months without a new government for Thailand, Parliament convened on Tuesday to attempt to choose a prime minister again.

Pheu Thai’s candidate, former property developer Srettha Thavisin, was the only name put forward by party leader Chonlanan Srikaew.

Pheu Thai launched the bid to form the government after it assembled an 11-party coalition including two parties allied with its former military adversaries, holding 314 seats in the 500-member House of Representatives.

Mr Srettha needs some support from the non-elected Senate, appointed by a previous military government, to achieve a majority in the combined parliamentary vote.

Both houses of Parliament vote together for the prime minister under the military-implemented constitution, in an arrangement designed to protect conservative military-backed rule. Senators, like the army, see themselves as guardians of traditional conservative royalist values.

House Speaker Wan Muhammad Noor Matha has allocated time for politicians to debate on the nomination before the vote takes place in the afternoon.

Mr Srettha did not run for office and the law does not require a prime ministerial candidate to be an elected politician. Parliament also does not require him to be present at the vote.

Pheu Thai has been heavily criticised by some of its supporters for backtracking on a pre-election pledge not to join hands with pro-military parties.

Party officials have defended the decision by saying it was necessary to break the political deadlock and seek reconciliation after decades of deep political divisions.

Mr Thaksin was ousted while he was abroad in 2006.

He returned to Thailand briefly in 2008 to face a court trial before fleeing the country.

He has avoided returning over concerns that he would not be treated fairly by the military-backed government and establishment that has long held a sharp animosity toward him.

He has remained active in Thai politics, however, often making video calls to rallies of his supporters and parties backed by him.

Napon Jatusripitak, a political science researcher and visiting fellow at Singapore’s ISEAS-Yusof Ishak Institute, said: “Thaksin’s plans to return to Thailand were postponed after the election results were announced – this implies a strong connection between the election, formation of coalitions, and selection of the prime minister on one hand, and Thaksin’s personal agenda on the other.

“Thaksin has managed to make this election about himself personally, and the direction of a Pheu Thai-led coalition heavily depends on his personal whims.”

Mr Thaksin could end up serving prison time unless he receives a royal pardon.

Deputy Prime Minister Wissanu Krea-ngam, of the outgoing military-linked government, has said Mr Thaksin is eligible to request a pardon and could receive special treatment because of his age.

Mr Napon said Mr Thaksin’s decision to return now suggests that “he has received assurances that he will not have to serve a prison sentence in full”.