Five tumultuous years after a military coup divided this Southeast Asian kingdom, Thailand held pivotal elections on Sunday that will determine whether it can end the long-running political crisis that has shattered its reputation for stability.

Many people fear the ballot, the first since last year’s anti-government demonstrations brought Bangkok to its knees, could trigger a new era of upheaval if the results are not accepted by rival protesters or the coup-prone army.

Television stations reported long lines at polling stations nationwide as registered voters chose a new 500-member parliament. Security was tight, with around 170,000 police deployed nationwide to protect booths, but no incidents of violence were immediately reported.

Opposition leader Yingluck Shinawatra, whose Pheu Thai party is considered a strong front-runner, was among the first to vote, dropping her ballot into a sealed green metal container in the capital, Bangkok. She thanked her supporters and called on voters to come out in high numbers.

Campaigning ended on Saturday night, and a ban on soliciting votes extends to the use of social media such as Twitter and Facebook.

The Election Commission is expected to announce preliminary results Sunday night.

While the poll itself is a race between Yingluck and ruling Democrats led by Prime Minister Abhisit Vejjajiva, it has come to be viewed as a referendum on the divisive legacy of former premier Thaksin Shinawatra, Yingluck’s exiled elder brother. Thaksin’s overthrow in 2006 set the nation on a downward spiral from which it is still struggling to recover.

Now living in Dubai to escape a two-year prison sentence on graft charges, Thaksin’s ascent to power in 2001 touched off a societal schism between this Southeast Asian nation’s haves and have-nots, between the marginalized rural poor who hailed his populism and an elite establishment that sees him as a corrupt, autocratic threat to the monarchy and the status quo.

That schism is playing out Sunday at the ballot box, and much is at stake.

Thailand “is at a crossroads,” said Siripan Nogsuan Sawasdee, a political scientist at Bangkok’s Chulalongkorn University. If the results are not respected, “we’ll be back to ground zero, more protests and more violence.”

And, many fear, more bloodshed, worse perhaps than last year’s anti-government demonstrations in Bangkok, which left more than 90 people dead and the city of glass high-rises and decaying apartment blocks in flames.

Local polls have consistently given Yingluck’s opposition party a strong lead, meaning 61-year-old Thaksin may “win the elections ... in absentia,” said Thitinan Pondsudhirak, director of Chulalongkorn’s Institute of Security and International Studies.

But the predictions have given neither Pheu Thai nor the ruling Democrats the 250-seat majority needed to form a government, meaning there will likely be fierce jockeying to win over smaller parties to build a governing coalition.

The question haunting this nation of 66 million people, known to tourists as “the Land of Smiles”, is what comes next?

Will the army and the monarchy accept a pro-Thaksin government or Thaksin’s potential return? Will the opposition accept a continuation of Abhisit’s rule if he manages to stay in power? Will the losing side take to the streets? Will there be a coup?

After Thaksin was ousted amid accusations of corruption and alleged disrespect to the king, his supporters regrouped and won the country’s last election in 2007. But the two pro-Thaksin premiers who filled his shoes were forced from office in controversial court rulings handed down after enraged “Yellow Shirt” demonstrators took to the streets, at one point shutting down both of Bangkok’s international airports, stranding hundreds of thousands of travellers.

When Abhisit came to power in the army-pressured political manoeuvrings that followed, it was the opposition “Red Shirts” who protested, first overrunning a regional summit in 2009 that saw heads of state evacuated off a hotel rooftop, then staging last year’s two-month demonstration, which paralyzed the capital.

All this has taken place against the backdrop of growing concern about a smooth royal succession. Ailing 83-year-old King Bhumibol Adulyadej has been hospitalized since 2009, and any shift in the constitutional monarchy’s traditional balance of power could have far-reaching consequences.

On Thursday, army chief Gen. Prayuth Chan-ocha reiterated his vow to stay neutral in Sunday’s vote, dismissing rumors the military would intervene.

But with hardened rivals further apart than ever, Thitinan said “the signs and signals” for a peaceful resolution is not good. If anything, they “have pointed to more army intervention,” he said.

“The issue is whether they (the army) would be willing to make a deal, whether they would be willing to make some accommodation” with the opposition, Thitinan said. Some speculate Yingluck would be allowed to take power in exchange for an agreement not to prosecute soldiers who took part in the coup or last year’s crackdown.

Last month, Prayuth urged voters to cast ballots for “good people”, comments widely interpreted as a veiled attack on the opposition and a plug for Abhisit.

The tide of recent history, though, is not on Prayuth’s side. Thaksin and his proxies have won the country’s last four elections. Abhisit’s Democrat party, by contrast, has not won a popular vote since 1992.

Siripan said Thailand’s military and elite upper classes are “trapped in an old illusion of Thailand that is not compatible with democracy.”

“They don’t want to adapt,” Siripan said. They want to safeguard their own status quo and “they’re not aware that people have changed, that society has changed” over the last five years. People are more educated, more politically active, more aware of their rights, she said.

Although Thaksin is credited for opening the door to such change, he is “hardly a model when it comes to promoting democracy,” said Pavin Chachavalpongpun of the Institute of Southeast Asian Studies in Singapore.

Though some see him as a hero to the poor, Thaksin exhibited a sharp authoritarian streak in office and was accused of corruption, cronyism and abuse of power.

Though Thaksin today lives thousands of miles (kilometres) away from Thailand, but there is little doubt who controls the opposition. Their campaign slogan is “Thaksin Thinks, Pheu Thai Acts.”

Oxford-educated Abhisit, meanwhile, has declared the vote “the best opportunity to remove the poison of Thaksin from Thailand” once and for all. He has also used his campaign to blame opposition protesters for burning Bangkok last year, saying a vote for Yingluck would be a vote for chaos.

More In: International | News