Election Commission secretary-general Puchong Nutrawong said the commission has instructed staff to halt voting if there is rioting or other violence.
"We don't want this election to be bloody. We can get every single agency involved to make this election happen, but if there's blood, what's the point?'' Puchong told Reuters. "... If there is continued obstruction, I pray only that there is no fighting and no coup.''
The military has stayed firmly on the sidelines so far, in contrast to the past. It has a history of having staged or attempted 18 coups in 81 years of on-off democracy.
Yingluck's party is bound to win the election, though without enough members to achieve a quorum in parliament, guaranteeing further stalemate, at best, even if the election passes off peacefully.
The Democrat Party is boycotting Sunday's poll and backs the protests.
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Election commissioner Somchai Srisutthiyakorn wrote on his Facebook page about the possibility of the poll being voided altogether.
"After the Feb. 2 vote, there will be people filing lawsuits for the election to be voided immediately, citing various reasons that they will put forward, such as the general election must be held on one day or violate the constitution, which would make it likely that 3.8 billion baht ($115 million) will have been spent for nothing,'' Somchai wrote.
Puchong said the commission was doing its best to adhere to the law and any speculation about the vote being annulled was for the courts to decide.
The protesters, camped out at major intersections in the city and blocking key arteries, forced polling stations in 49 of Bangkok's 50 districts to shut last weekend and voting could only go ahead in three of 15 southern provinces. Some voters were physically pulled away from the polling booths.
Suthep wants to rid the country of the Shinawatra family's political influence and accuses Yingluck, who swept to power in the last election in 2011, of being Thaksin's puppet.
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The protesters say Thaksin is a corrupt crony capitalist who commandeered Thailand's fragile democracy, using taxpayers' money to buy votes with populist giveaways. Thaksin has chosen to live abroad since 2008 to avoid a jail term for graft.
He or his allies have won every election since 2001. His supporters say he was the first Thai political leader to keep campaign promises to help the poor.
Suthep wants to set up a "people's council'' of notable individuals before another election is held.
The prolonged unrest has hurt tourism and the central bank says the economy may grow only 3 percent this year, rather than the 4 percent it had forecast.