Thailand's first poll re-runs have passed peacefully following a widely disrupted general election, as pro-government "Red Shirts" stepped up rallies in support of Prime Minister Yingluck Shinawatra's battered administration.
The original February 2 election failed to ease a four-month political crisis when protesters seeking to topple Yingluck's government caused the closure of around 10 per cent of polling stations, many in opposition strongholds.
The Election Commission said results cannot be announced until polls have been held in all constituencies, setting a late-April deadline for their completion.
Yingluck can only remain prime minister in a caretaker role until then with limited power over policy, further eroding her authority as she handles ongoing street protests and a series of legal challenges against her administration.
Election commissioner Somchai Srisutthiyakorn said around 120,000 people were registered to vote on Sunday across more than 100 constituencies in five provinces.
He said the re-runs, the first attempted since February 2, had been held "peacefully... without any problems".
But only a trickle of voters were seen at several polling stations in Phetchaburi, an opposition heartland around 160 kilometres south of Bangkok, according to an AFP reporter.
"I was disappointed that I had the right to vote on February 2 but couldn't," Sangwan Yuusuk, 57, said at a polling station.
Under election law, 95 per cent of the 500 seats in the lower house of parliament must be filled to enable the appointment of a new government.
On its website the Election Commission said senators will be elected on March 30.
The main opposition Democrat party, which boycotted the general election, last month lost a legal bid to nullify the poll.
In addition to the protests, Yingluck faces a series of legal complaints against her government, including charges of negligence over a troubled rice subsidy scheme. These problems could see her removed from office.
Pro-government Red Shirts have ramped up their rallies and rhetoric in support of Yingluck and her billionaire brother Thaksin. He is a former prime minister who lives in exile to avoid jail for a corruption conviction.
Television footage on Sunday showed thousands of people grouping in a car park in Khon Kaen, a Red Shirt stronghold in the country's northeast. They were gathering for an overnight rally, wearing the ubiquitous red and waving flags.
This followed a similar rally on Saturday in the northeast, which together with the rural north has returned Shinawatra-allied governments to power in every election for more than a decade.
These loyalists say their votes are a political reward for policies that have funnelled state money to their regions after years of neglect.
Opponents describe the same policies as a form of vote-buying.
"We are ready to come into Bangkok if the situation is still a mess," Red Shirt spokesman Thanavut Vichaidit told AFP, as he led a convoy of supporters to Khon Kaen.
Thailand has been riven by political divisions since 2006.
The current rallies have killed 23 people - among them four children - and wounded several hundred others.
