'Involvement of a high-ranking member of the royal family in politics, in whatever way, is an act that conflicts with the country's traditions, customs, and culture, and therefore is considered extremely inappropriate,' the king said in a statement issued by the palace
Thailand's King Maha Vajiralongkorn said on Friday his elder sister's announcement she is running for prime minister in March elections is "inappropriate" and unconstitutional, likely sinking her candidacy for a populist opposition party.
Princess Ubolratana, 67, shocked the nation when she announced on Friday she would be the sole prime ministerial candidate for the party, which is loyal to ousted ex-premier Thaksin Shinawatra.
But the opposition from her younger brother, a constitutional monarch, is likely to lead to her disqualification by the Election Commission.
"Involvement of a high-ranking member of the royal family in politics, in whatever way, is an act that conflicts with the country's traditions, customs, and culture, and therefore is considered extremely inappropriate," the king said in a statement issued by the palace. The leader of a pro-military party in Thailand said on Friday its rival's nomination of the king's elder sister as its prime ministerial candidate may breach election law.
Paiboon Nititawan, the leader of the People's Reform Party, handed a letter to the Election Commission calling on it to decide whether to invalidate the nomination of Princess Ubolratana Rajakanya Sirivadhana Barnavadi.
He said the nomination could breach the law that prevents political parties from using the monarchy for campaigning.
Ubolratana relinquished her royal titles in 1972 after marrying an American fellow student, but she is still treated by officials and the Thai public as a member of the royal family.
The Election Commission is required to endorse or reject all candidates by next Friday.
Bridging the divide?
The military under Prayut has cast itself as the protector of the monarchy.
Ubolratana, a colourful, public-facing royal in contrast to her more restrained brother King Maha Vajiralongkorn, relinquished her royal titles after marrying the American Peter Jensen in 1972.
But the couple divorced and she moved back to Thailand where she is still considered part of the royal family.
In Thailand she experienced tragedy, losing her autistic son Poom to the 2004 Asian tsunami.
Thailand has not had a royal as premier since becoming a constitutional monarchy in 1932.
Known to the public for lead roles in Thai films, onstage singing performances, a vibran t fashion sense and a sizeable Instagram following, Ubolratana is the first-born child of the late King Bhumibol Adulyadej.
Analysts said she is not technically covered by the kingdom's royal defamation law - which carries heavy jail sentences - but that given the wide interpretation of the rules, she is unlikely to face the scrutiny given to most politicians.
"Who would dare criticise a royal prime minister?" said Puangthong Pawakapan, professor of political science at Chulalongkorn University.
The stride into politics by a royal has left Thais scrambling to work out what it may mean for the nation's tattered democracy.
"This is quite unprecedented and nobody is prepared for this," Professor Anusorn Unno, of Thammasat University, told AFP.
"I don't think it's the victory for the people; I think this is part of the adaptation of the ruling elite in terms of changing the landscape of politics."
Since ascending the throne in 2016, King Maha Vajiralongkorn has reorganized palace affairs.
The vastly wealthy Crown Property Bureau is now under his personal stewardship, he has appointed several new privy counsellors and established a highly trained personal guard.
Crucially he has appointed a new army chief from a different faction of the military to the ruling junta.
His coronation will be held in May.