BANGKOK - Thailand's biggest political party, hit by defections ahead of an election that will allow the kingdom to emerge from military rule, remains confident of its chances even as a new polling system threatens to confuse longtime supporters.

"This election has been designed for a return to democracy while keeping a dictatorial government. It's like dictatorship under the veil of democracy," said Dr Sudarat Keyuraphan, who leads the Pheu Thai Party's election strategy committee.

The 57-year-old former agriculture minister sat out of politics for most of the past decade before being parachuted into what is arguably the party's top position this year.

Shielded from Pheu Thai's legal troubles by her exclusion from executive positions, she has been steering the mothership while several high-profile members moved to smaller, allied parties to maximise their chances of being elected under the new Constitution.

While Dr Sudarat doubts supporters will abandon Pheu Thai, she admits it is a tough job getting voters to understand what is at stake.

The ruling generals maintain a partial ban on political activity and explicitly outlaw electioneering, even while the country gears up for a poll tentatively set for Feb 24.

"Most of the people think the election system is the same as usual. But it's not," she said in an interview with The Straits Times last Friday (Dec 7).

New rules tighten the proportional representation system to the detriment of big parties like Pheu Thai. On ballot sheets, specific numbers will no longer be assigned to each party on a nationwide basis, making it harder for voters to identify the party that they want to vote for.

The future prime minister will be selected not solely by the 500-seat elected Lower House, but jointly with 250 appointed senators, within a transitional five-year period.

Analysts widely expect senators to work with pro-junta parties to prolong the premiership of Prime Minister Prayut Chan-o-cha, who came to power after staging the 2014 coup.

Dr Sudarat, who last month pipped Mr Prayut to top a poll on who people wanted to see as prime minister, urged voters to be "strategic" at the ballot box.

"No matter whether you like or don't like us, please vote for us. At the very least, if you vote for us and we don't do a good job, you can kick us out."

By her count, 28 Pheu Thai politicians have crossed over to pro-junta parties so far, something she attributes to strong-arm tactics.

"We saw this after the 2006 coup when more than 50 per cent of our members of parliament were pressured to go over to the other side," she said, recalling the legislative upheavals after then prime minister Thaksin Shinawatra - leader of the Thai Rak Thai Party at the time - was ousted in 2006.

After the party was dissolved by a court order in 2007, its politicians and allies regrouped under the banner of People's Power Party (PPP). The PPP won the most seats in the 2007 election, only to have its ruling coalition crumble under defections.

When the PPP was dissolved by a court ruling in 2008, its remaining politicians moved to the Pheu Thai Party, which won by a landslide in the 2011 general election. Then Pheu Thai was thrown out by the 2014 coup.

Dr Sudarat, as former deputy leader of Thai Rak Thai, served a five-year political ban that ended in 2012, after which she turned down an invitation to work in Pheu Thai.

This time, however, she could not say no. "It's like the house has been rocked by several bombs. It needs to be restored," she said.

Thaksin remains in the public eye despite living in self-exile for the past decade to avoid jail time for conflict of interest. Among the royalists and urban middle class, he is reviled as a corrupt politician whose populist policies that enticed the rural poor have challenged the established order.

Addressing the pervasive view that 69-year-old Thaksin continues to control Pheu Thai through proxies, Dr Sudarat said "those who took power" have demonised Thaksin to stoke fear.

Thaksin, she said, "is a Thai, an ageing one. His relatives are still in Thailand and his grandchildren were born and are growing up in Thailand. As a former prime minister, he of course hopes to see Thailand develop alongside neighbouring countries".

Asked what she made of Thaksin's only son, television station owner Panthongtae Shinawatra, joining Pheu Thai last month, she described the latter as only a "supporter".