The closely watched polls are expected to propel the National League for Democracy (NLD) leader into parliament for the first time, marking a dramatic return to mainstream politics for her party after years on the sidelines.
But Sunday's by-elections could also highlight the pro-democracy champion's uneasy relations with restive ethnic minorities who bore the brunt of the generals' repression during almost half a century of military rule.
In Shan state, wedged between China, Laos and Thailand to the east and the rest of Myanmar to the west, the NLD's main rival appears to be not the ruling "lions" but the "white tiger" Shan Nationalities Democratic Party.
"I will support the white tiger," said Nann Muu, a 35-year-old farmer from a village in Lashio township. "I do not know Aung San Suu Kyi," she said.
The SNDP came second behind the NLD in a 1990 election whose result was never recognised by the then military rulers.
It is now the second-biggest party in parliament, thanks to a strong showing in vast Shan state -- home to six million people -- in a 2010 election that was marred by complaints of fraud and by the exclusion of Suu Kyi.
Its leaders are confident they can repeat their success in Sunday's vote, which is to replace lawmakers who gave up their seats in parliament to join a nominally civilian government dominated by former generals.
"Whenever we visited villages, people welcomed us gratefully and supported us," said Sai Aung Sar, a senior SNDP official in Lashio. "We don't worry that the NLD is participating in this election.
"Aung San Suu Kyi has been travelling around the country with her kindness for the people. Whoever participates, it's good if they work for the country and people."
With only two seats at stake in Shan, out of 45 available in Sunday's vote, it is unlikely to be a pivotal battleground, and in any case the by-elections cannot threaten the ruling party's majority in parliament.
But a defeat for the NLD in Shan would make it harder for the party to claim to enjoy the support of the nation's various ethnic groups, and would do little to soften the Nobel laureate's image as an ethnic-majority leader.
Civil war has plagued parts of the country formerly known as Burma since it won independence from Britain in 1948.
An end to the conflicts and alleged rights abuses involving government troops is a key demand of Western nations that have imposed sanctions on the regime.
"The extent to which minority communities feel discriminated against is often not well understood by the Burman majority," said Jim Della-Giacoma, Southeast Asia project director at the International Crisis Group think-tank.
Suu Kyi is well regarded in ethnic communities, but "many minority people see her first and foremost as a member of the Burman elite".
He said Sunday's vote represented a "lost opportunity" for the NLD to join hands with ethnic minority parties in areas where they are strongest.
"The decision by the NLD to run in all seats and the belief that it could win in all seats did antagonise some minor and ethnic groups. They probably have legitimate worries that their interests will be trampled on as the NLD tries to find its own place in the corridors of power," Della-Giacoma said.
It is a perception that NLD candidate Sai Myint Maung, a 65-year-old lawyer, is striving to dispel.
"I've been telling voters that the NLD is not a Burman party or a Shan party. The NLD is the party of all ethnicities," he said.
There are signs that the efforts are bearing fruit, even though the local NLD candidates are not well known in Shan state, home to various ethnic groups and several rebel armies.
"I voted for the white tiger in 2010. But this time, many will vote for Daw (Aunt) Suu. I hope she will work for us to have a better ethnic life," said Sam Nap, a 46-year-old ethnic Wa who is a traditional doctor.
The government has agreed tentative ceasefires with many of Myanmar's rebel ethnic groups, but ongoing fighting in northern Kachin state that has displaced tens of thousands of people has cast a shadow over the peace process.
On Friday the authorities postponed the by-elections in three Kachin constituencies, citing security concerns, barely a month after Suu Kyi herself campaigned in the region.
There has been speculation that if she wins a seat in parliament Suu Kyi could take on a role as mediator between the government and the rebels, but observers say the opposition leader is likely to tread cautiously.
"She can't be seen to be too close to ethnic minority political interests, nor can she be seen to be endorsing some of the policies that have been implemented in many ethnic minority areas, "said Nicholas Farrelly, an expert on Myanmar issues at Australian National University.
The ethnic issue "strikes at the heart of the difficulties that Burma and its politicians are likely to face in the years ahead", he said.