UN chief Ban Ki-moon called Thursday for the upcoming crucial election in Thailand to be conducted peacefully and in a "fair, credible and transparent" way.
UN Secretary General Ban urged all parties to refrain from violence before, during and after the July 3 poll and "to accept and respect the will of the people as expressed at the ballot box," his spokesman said in a statement.
Amid fears the vote could bring unrest, more than 430 candidates have sought protection, according to police, and more than 170,000 police officers are due to be deployed to protect polling stations on voting day.
The ruling Democrat party, led by Prime Minister Abhisit Vejjajiva, is locked in a tough battle with the main opposition party Puea Thai, led by the sister of Thaksin Shinawatra, who was ousted in a coup in 2006.
The country has since suffered from deep political divisions and a series of street protests by rival groups.
Ban "expects the elections will be conducted peacefully and in a fair, credible and transparent manner so as to contribute to reconciliation and the consolidation of democratic norms in the country," his spokesman said.
The fugitive ex-premier Thaksin remains a hugely divisive figure in Thailand, hated by the Bangkok-based elites, who fear he could try to return a free man if his sister Yingluck Shinawatra wins, as the polls predict.
He lives in self-imposed exile in Dubai, having fled in 2008 before a Thai court sentenced him in absentia to two years in prison for corruption, and he is also wanted for criminal charges including terrorism.
That accusation links to protests by his working-class "Red Shirts" supporters, whose mass opposition protests in Bangkok last year turned deadly, ending after two months with an army crackdown and more than 90 people dead.
Many observers fear a resurgence of street demonstrations by rival groups over the coming months, and US policymakers are worried the vote may set off new instability that diminishes the role of Washington's oldest Asian ally.
Many are also looking at the moves of the powerful Thai army, no stranger to intervention in politics after 18 actual or attempted coups since 1932.
Military chief General Prayut Chan-O-Cha has pledged to be neutral in the election but he has also called on the electorate to cast votes for "good people" -- an outburst taken as an attack on Yingluck.
Earlier this week, four soldiers were arrested in a crucial northeastern political battleground for allegedly intimidating opposition activists ahead of the vote, police said.
Another factor is the country's long tradition of electoral irregularities, such as vote-buying, with only one international monitoring group and no foreign governments sending observers to polling stations.