Thai billionaire and ex-Prime Minister Thaksin Shinawatra,

who has dominated Thailand’s politics for over two decades, has announced plans to return to the country in July. This announcement has caused a stir as voters prepare to go to the polls in a general election on Sunday, with potential implications for the vote and the horse-trading afterwards to form a government.

Thaksin’s daughter, Paetongtarn Shinawatra, is the leading prime ministerial candidate for the opposition Pheu Thai party, which is made up of loyalists to the populist movement that first swept her father to power in 2001. However, if Thaksin returns, it could complicate the post-election scramble by Pheu Thai to try to form a coalition with other opposition parties to end military domination of politics.

Thaksin Shinawatra, who faces prison from convictions he says were politically motivated after his ouster, would have to make a deal with at least some elements of the pro-military establishment that has ousted him and his family from the prime minister’s office three times to be able to return to Thailand.

“The announcement could hint that Pheu Thai is seeking a deal that could see them join up with their former rivals in order to get Thaksin home,” said Titipol Phakdeewanich, dean of the faculty of political science at Ubon Ratchathani University.

Thaksin Shinawatra has been at the center of Thailand’s political scene for years, causing bloody chaos with rival street protests between his supporters and opponents. The army has staged two coups, and courts have intervened to remove pro-Thaksin governments and dissolve parties loyal to him. Yet, his reconstituted parties keep on winning elections.

In Sunday’s vote, Pheu Thai is widely expected to win the most seats in the 500-seat House of Representatives. However, because of military-written rules, it could struggle to form a coalition because a 250-seat Senate appointed during military rule also gets a vote for the prime minister.

Those Senate votes were key to Prime Minister Prayuth Chan-ocha retaining power in the last election four years ago, even though Pheu Thai won the most seats. This time, Pheu Thai is polling strongly along with the progressive, youth-oriented, Move Forward party.

Together, the two opposition parties could get as many as two-thirds of lower house seats, putting them close to the 75% needed to overcome the Senate’s 250 votes. And with some Senate members recently showing a willingness to defy the government, the numbers could add up to a Pheu Thai-Move Forward coalition that excludes pro-military parties.

Pheu Thai’s Paetongtarn has vowed she would never join with pro-military parties and expressed a willingness to join with Move Forward in a coalition. But bringing her father home may ultimately be the deciding factor for Pheu Thai, forcing it into a deal with the establishment.

“For Thaksin to come home, there has to be a deal. He can’t just walk into Thailand,” said Thitinan Pongsudhirak, a political scientist at Bangkok’s Chulalongkorn University. “Post-election, Pheu Thai will be biding its time and looking for a deal. That’s why I think the likelihood of Pheu Thai going with Move Forward is very slim.”

Conservatives might be willing to make a deal and allow Thaksin to return, as after so much time and turbulence, many in the establishment had concluded that it is no longer worth fighting Thaksin. In fact, the populist policies that were once seen as so radical have been mainstreamed into almost all parties including pro-military ones.

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