BANGKOK (REUTERS, XINHUA) - The sister of Thailand's king said on Friday (Feb 8) she was exercising her rights as a citizen in accepting a political party's nomination for prime minister in a March general election.

"I have relinquished my royal titles and lived as a commoner," Ms Ubolratana Rajakanya Sirivadhana Barnavadi, 67, said in a post on her Instagram account.

"I have accepted the Thai Raksa Chart Party nomination for prime minister to show my rights and freedom without any privileges above other fellow Thai citizens under the Constitution," she said.

"I have undertaken this action with sincerity and a resolve to sacrifice for a chance to lead Thailand toward progress and prosperity," she added.

The former princess is the eldest child of the late King Bhumibol Adulyadej and elder sister of His Majesty King Maha Vajiralongkorn.

On the same day, Thai Raksa Chart also confirmed Ms Ubolratana is a commoner and is fully eligible to run for the prime minister after a rival party asked the Election Commission (EC) to check whether it is rightful to nominate a member of the royal family, as an election campaign will involve using the former princess' portraits which may be against the election rules.

Meanwhile, EC secretary general Charungwit Phumma confirmed that all verified candidates for the prime minister may have their portrait or picture and name shown on campaign posters and banners of their respective contestant parties.