Puea Thai Party's Yingluck Shinawatra greets her supporters during the election campaign.

Puea Thai Party's Yingluck Shinawatra greets her supporters during the election campaign. Photo: Reuters

Thailand is precariously poised between forces of democracy, militarism, monarchy and corruption. Lindsay Murdoch reports from Bangkok.

DEEPLY polarised Thais will vote tomorrow in an election where the losing side is unlikely to accept the result, prolonging a six-year political crisis in the ''Land of Smiles''.

Thailand is at a crossroads, facing options of democracy or military domination. Powerful influences are in play, including exiled billionaire former prime minister Thaksin Shinawatra, seen by Bangkok's ruling elite as authoritarian, corrupt and a threat to the country's revered monarchy.

Reports of secret back-room deals with military commanders and a powerful interfering ''hidden hand'' in Thai politics have been circulating for weeks, stoking tensions 14 months after 91 people were killed in Bangkok street clashes.

The Puea Thai (For Thais) party controlled by Mr Thaksin has surged in pre-election polls, holding sway in its provincial strongholds and taking the lead in pivotal swing constituencies. Led by Mr Thaksin's photogenic younger sister Yingluck Shinawatra, the party looks like winning the majority of seats in the 500-seat parliament, giving it the first chance to form government.

The party will probably be able to recruit the smaller Chart Thai Pattana Party controlled by banned politician Banharn Silpa-archa to gain a parliamentary majority. But many of Bangkok's business and government elite, backed by the military, will plot to undermine a government controlled by Mr Thaksin, a telecoms tycoon who was ousted by the military in 2006.

Army commanders have exerted influence in the past to deny power to Mr Thaksin, who from his base in Dubai has reportedly made overtures to the royal palace.

If Puea Thai can form government its politicians are certain to face legal and constitutional challenges, including Ms Yingluck, who has already being accused of perjury in an asset-concealing case involving $US1.4 billion ($A1.3 billion) of her brother's fortune.

One group has asked the Election Commission to disband Puea Thai on the grounds that it is run illegally by Mr Thaksin, a banned politician and convicted felon.

Despite being a political novice, Ms Yingluck, 44, ran an effective campaign, promising populist programs such as cheap healthcare, a debt moratorium, minimum wage increase, a price guarantee for rice and welfare for the elderly.

She is poised to become Thailand's first woman prime minister.

Puea Thai's unspoken aim is Mr Thaksin's political resurrection and to save him from serving a two-year jail term for alleged corruption.

If Puea Thai wins he would be encouraged to return, probably under amnesty, creating a possible flashpoint.

Another troubling scenario is if the Democrat Party, led by Prime Minister Abhisit Vejjajiva, manages to form government through underhand military-assisted horse-trading with other parties.

Mr Thaksin's supporters, known as the ''red shirts'', would mobilise mass protests if they see the establishment contriving to manufacture another Democrat-led coalition government. This time, though, the protests would almost certainly not be confined to Bangkok.

Andrew Walker, an expert on Thai politics at the Australian National University, said the Democrats have not won an election since 1992 and it was looking very unlikely they would win this one.

''The best the Democrats can hope for is that they can cobble together a coalition with the support of most, if not all, of the minor parties,'' he said. ''This would be a recipe for ongoing instability.''

Much is at stake for the Thai army, which has staged 18 coups or attempted coups since 1932. Army commanders will be worried that Mr Thaksin will take revenge against those involved in the coup that overthrew him if his party returns to power. The military has recently initiated charges against some of Mr Thaksin's supporters for alleged royal insults.

In a speech on June 14, the ultra-royalist General Prayuth Chan-ocha launched what was seen as an indirect attack on Ms Yingluck.

''Voters must not allow themselves to be blinded by the personalities involved and must not vote for politicians who violate morals and laws,'' he said.

But a source close to the military has claimed that Thaksin loyalists have been making overtures to senior officers of the Thai army's First Infantry Division with the aim of minimising the military's meddling after the election. The dominance of the First Infantry in top army positions was lost to the provincial-based Second Infantry after the 2006 coup.

There is also a report in the Asia Times website of high-level talks between the royal palace, Mr Thaksin and the military aimed at avoiding new confrontation and to foster reconciliation.

Mr Thaksin's camp appears to want a wider accommodation with at least one section of the royalist establishment, according to the report.

There is some good news as 40 million Thais go to the polls.

The health of revered King Bhumibol appears to be improving after recent surgery. Television has shown him taking photographs from his hospital wheelchair.

Forty-two parties contesting the election have also made some amazing promises to voters, including free tablet PCs, high-speed trains and tax cuts.

Dr Walker, a senior fellow at the ANU's college of Asia and the Pacific, said the election was a crucial test of Thailand's democracy.

''If this result is overturned, either by force or legal manipulation, it will be an invitation for hardliners to pursue violent alternatives,'' Dr Walker said.

''The bloody events of April-May 2010 were a taste of what the future may hold if powerful forces in Thailand continue to subvert electoral results.''