Any bloodshed would further undermine the credibility of a vote that is deemed incapable of restoring stability in the polarized country.
"The people will not close the polling booths, but will demonstrate on the roads. They will demonstrate calmly, peacefully, without violence. If anyone comes to try to cause trouble, we absolutely will not argue with them. We won't do anything that will hinder people from going to vote," Suthep said on Friday night.
"In the south, for those who are surrounding the places where ballots are being collected, surround them as usual, but I ask that you sit there peacefully, don't back down, don't run away, and do not fight them, just pray. I believe that this poll will be voided for sure."
The Nation newspaper said protesters were camping at post offices to block the delivery of ballot papers in the south, where support for Suthep is strongest.
Many protesters in Bangkok wore red, the color of Yingluck's "red shirt" supporters, in Saturday's march, after Suthep said no one had the right to hijack a color.
"In honor of Chinese New Year, let's wear red on our walk in Yaowaraj (Chinatown)," said Suthep, wearing a festive red Chinese shirt.
(Read more: Why Thailand's political strife is far from over)
The United Nations in Thailand called for a peaceful vote. Ten people have died and at least 577 have been wounded in politically related violence since late November, according to the Erawan Medical Center, which monitors Bangkok hospitals.
The anti-government protesters took to the streets in November in the latest round of an eight-year conflict between Bangkok's middle class, southern Thais and the royalist establishment against the mostly poor, rural supporters of Yingluck and her brother, former premier Thaksin Shinawatra, who was ousted in 2006.
The main opposition Democrat party, which backs the anti-government protests, is boycotting the election, which Yingluck's party is bound to win, though without enough members to achieve a quorum in parliament, guaranteeing further stalemate, at best, even if the election passes off peacefully.
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.