The Thai Raksa Chart Party threw election politics into chaos on Friday when it nominated Princess Ubolratana as its candidate to be prime minister.

The party officially registered the elder sister of His Majesty King Maha Vajiralongkorn as news people pushed for vantage points at the Office of the Election Commission.

The move was the focus of election rumours on Thursday and overnight, but no media had been bold enough to mention her name or the royal connection until the actual event at 9am Friday.

Executives of the party arrived at the EC office at the Government Complex after announcing they would have only one candidate for prime minister - what they called "an important person outside the party".

As they checked in at the EC office, they showed an army of reporters a document confirming Princess Ubolratana, 67, as their candidate as prime minister.

The move is a serious blow to plans by Prime Minister Prayut Chan-o-cha and the Palang Pracharath Party (PPRP) to extend power via the March 24 elections.

PPRP officially registered Prime Minister Prayut Chan-o-cha as its prime ministerial candidate, but the nomination of Princess Ubolratana completely overwhelmed his nomination.

Thai Raksa Chart is a spinoff from the Pheu Thai Party, and both are friends of the fugitive former prime ministers Thaksin and Yingluck Shinawatra.

Princess Ubolratana has been seen with the Shinawatra brother and sister in public, notably at the most recent World Cup tournament in Russia.

The Thai Raksa Chart statement issued with her nomination said the party was greatly honoured that the princess had accepted its invitation.

The princess had graduated with bachelor’s and master’s degrees from leading universities in the United States -- Massachusetts Institute of Technology and the University of California, Los Angeles -- and initiated the To Be Number One project to protect the young from drug abuse. 

She understood the plight of people, the party said.

The princess had helped promote Thai tourism for over a decade and had decided it was time to work for the nation and people through the role of the prime minister, the party statement said.