The eldest sister of Thailand's King Maha Vajiralongkorn has joined the race to be the country's next prime minister.
Princess Ubolratana Mahidol, 67, will stand for a party allied to ousted prime minister Thaksin Shinawatra, according to registration papers.
Traditionally the Thai royal family stays out of politics, so this is an unprecedented move.
Thailand's election is scheduled to take place on 24 March.
The princess, who relinquished her royal title in the 1970s, has registered for the Thai Raksa Chart party.
"The party [board] agrees that the name of Princess Ubolratana, an educated and skilled person, is the most suitable choice [for premier]," said Preechapol Pongpanich, leader of the Thai Raksa Chart party, according to an AFP report.
The development raises questions about the future of other political candidates, amid speculation that no-one will run against a member of the royal family.
In an astonishing move the elder sister of King Vajiralongkorn has submitted her name as the Prime Ministerial candidate for a party allied to former PMs Thaksin & Yingluck Shinawatra. As a royal, in reality, she cannot be opposed. This completely upends Thai politics.— Jonathan Head (@pakhead) February 8, 2019
The country's current prime minister, Prayuth Chan-ocha, also announced on Friday that he would be running for prime minister in the current election.
The army chief, who seized power in a military coup in 2014, will be running as a candidate for the pro-military Palang Pracharat party.
Why does this election matter?
Thailand's military has a history of intervening in politics and has seized power 12 times since the end of the absolute monarchy - and the introduction of the first constitution - in 1932.
The March vote will be the first since Mr Prayuth overthrew the democratic government and ousted ex-Prime Minister Yingluck Shinawatra, the younger sister of Thaksin Shinawatra.
Both Mr Shinawatra and his sister currently live in self-imposed exile.
In 2016, Thais voted to approve a new constitution created by the country's military leaders, which was designed to perpetuate military influence and block Mr Thaksin's allies from winning another election.
But according to the BBC's Bangkok correspondent Jonathan Head, that strategy is "in pieces" now that Princess Ubolratana has put her name forward.
Who is Princess Ubolratana Mahidol?
- Born in 1951, Princess Ubolratana Rajakanya Sirivadhana Barnavadi is the oldest child of Thailand's late King Bhumibol Adulyadej.
- After marrying an American in 1972, she gave up her royal title and moved to the US. After her divorce she returned to Thailand and once again started participating in royal life.
- The princess engages actively in social media and has also starred in several Thai movies.
- She had three children, one of whom died in the 2004 tsunami while the other two still live in the US.