Thailand's political parties prepared for rallies on Friday in a final push to galvanise support and woo the undecided ahead of a Sunday election when voters will choose whether to stay the course with military-linked conservatives or opt for change.

Prime Minister Prayuth Chan-ocha, a former army chief who ushered in years of military rule with a 2014 coup, is hoping to lead conservative forces to victory over an opposition led by the populist Pheu Thai party, backed by the billionaire Shinawatra family.

The rivalry between pro-military, royalist conservatives and a brash, technocratic opposition has defined Thai politics for nearly 20 years, much of it in turmoil that has included bloody street clashes and two coups.

The latest opinion polls show parties led by Prayuth and his coalition allies trailing Pheu Thai and another opposition party, Move Forward.

"A Pheu Thai landslide will change the country instantly," Srettha Thavisin, a property tycoon and one of Pheu Thai's prime ministerial candidates, told a crowd through a loudspeaker on the back of a truck late on Thursday.

While the rivalry between old and new political forces is at the forefront of many voters' minds, the economy is also looming large in a country heavily reliant on tourists that was battered by the COVID-19 pandemic.

The tourists, and growth, are making a comeback but high levels of household debt are clouding the outlook and all parties are promising bold fixes.

 

WINNING ELECTIONS

Pheu Thai and its previous incarnations have won every election for 20 years. It wants a landslide this time to ensure no repeat of the last polls in 2019, when it won the most votes but was not allowed to form a government due to electoral rules drafted under military rule.

Two of the party's former prime ministers, Thaksin Shinawatra, and his sister, Yingluck Shinawatra, are in self-imposed exile after being ousted in coups.

Thaksin this week said he was hoping to return home in July after 17 years.

His youngest daughter, Paetongtarn, 36, is another Pheu Thai nominee for premier.

Prayuth, 69, has been campaigning hard with his newly former United Thai Nation party, urging voters to hold firm with him.

"We must be united. I want to see this country in peace," Prayuth told a rally in the south.

Move Forward, a progressive opposition party, is seeing a late stage surge and is banking on young voters with promises of big change, from tackling monopolies and ending military conscription to amending a strict law on royal insult that critics say is used to stifle dissent.

"We have 300 policies ready to change the country," its leader, Pita Limjaroenrat, said in a debate.

But a big question hanging over the election is whether the military-dominated establishment will let the will of the people take its course with the formation of a new government.

Under the 2017 constitution drafted by the military, the party that wins the most seats in the 500-seat House of Representatives could struggle to form a coalition because a 250-seat Senate also votes for the prime minister.

There's always a possibility of a return to street protests if a party that wins big in the vote is denied the chance to take power by rules that many critics say were devised to enshrine military influence over civilian politics.

(Editing by Martin Petty, Robert Birsel)