UN Secretary General Ban Ki-moon raised concerns about obstruction of voting in Sunday's general election, and urged all parties to resolve their differences through dialogue.
"Any action that undermines democratic processes and hinders the democratic right of the Thai people cannot be condoned," he said of the political deadlock.
Anti-government protesters staged demonstrations and blocked the delivery of ballots to polling stations Sunday, causing the vote to be cancelled in nearly 10 per cent of the 90,000 polling stations nationwide.
The Election Commission has indicated that it may take several weeks before the electoral process is completed.
"While he recognises the complexity of the situation and that some chose not to participate in the election, the secretary-general is concerned that a number of Thai people were not able to exercisetheir right to vote," the UN press statement said.
The People's Democratic Reform Committee has been holding nearly daily protests in Bangkok for the past three months to try to force caretaker Prime Minister Yingluck Shinawatra and her cabinet to resign.
It is trying to create a political vacuum that could lead to an appointed interim government to make political reforms before any new election.
There are fears that the deadlock between protesters and the caretaker government could lead to a military coup, of which there have been 18 in Thailand over the past eight decades.