BANGKOK (REUTERS) - The Thai King's sister, disqualified this week by the Election Commission from running for prime minister, apologised on Tuesday (Feb 12) for causing "problems" for the Thai people ahead of next month's election, the country's first since a 2014 coup.

Princess Ubolratana Rajakanya Sirivadhana Barnavadi's comments came a day after the commission dropped her name from an official list of prime minister candidates.

The commission said members of the royal family should stay above politics, echoing a sharp rebuke from King Maha Vajiralongkorn that her bid was "inappropriate" and unconstitutional.

"I am sorry my genuine intention to work for the country and Thai people has caused such problems that shouldn't have happened in this era," she said on Instagram late on Tuesday, after making a public appearance in central Thailand.

She ended her statement with the hashtag, "#howcomeitsthewayitis".

Some social media users urged her to serve the people as a member of the royal family, but Princess Ubolratana responded: "I don't want to be in that position anymore. I gave that up a long time ago."

Princess Ubolratana's unprecedented nomination by a party allied with populist former premier Thaksin Shinawatra unsettled the South-east Asian nation, where the monarchy is revered by millions of Thais and remains above politics.

The Election Commission is also considering dissolving the Thai Raksa Chart party as a result of the nomination.

Electoral laws forbid involving the monarchy in political campaigns.

The party urged the body to be fair in its ruling.

"The constitution protects the rights and liberty of the Thai Raksa Chart party as the accused," Mr Surachai Chinchai of the party's legal team, said in a statement on Wednesday.

"We urge you to give Thai Raksa Chart a chance to object and show supporting evidence within a suitable period of time," he said.

The Thai Raksa Chart party is an offshoot of Thaksin's Pheu Thai party. Thaksin-linked parties have won every general election since 2001.

The March 24 election is set to be a showdown between the military-backed, royalist Prime Minister Prayut Chan-o-cha and supporters of Thaksin, who was ousted in a 2006 coup and forced into exile, but remains immensely popular.