On Friday, 67-year-old Ubolratana Rajakanya Sirivadhana Varnavadi was put forward as a candidate for prime minister in Thailand’s upcoming elections. A former U.S. resident, Ubolratana is a well-known public figure in Thailand who has more than 100,000 followers on her private Instagram account.

If she is approved as a candidate in March’s election, however, Ubolratana may cause chaos in Thai politics. That’s because she is officially known as Princess Ubolratana, the elder sister of Thai King Vajiralongkorn. In Thailand, the royal family is held in high regard, and criticizing the king and his successor is harshly punished under the country’s lèse-majesté laws.

Unlike in other countries where the royal family is widely mocked (Britain) or more or less ignored (Norway), Thai law makes it illegal to defame, insult or threaten “the King, the Queen, the Heir-apparent or the Regent.” The Thai constitution also says: “The King shall be enthroned in a position of revered worship and shall not be violated. No person shall expose the King to any sort of accusation or action.”

Though other countries still have similar laws — both Spain and the Netherlands have lèse-majesté laws on the books — Thailand’s enforcement of its laws may make them the strictest in the world. The punishment under Section 112 of the legal code is imprisonment from three to 15 years; a single person can sometimes face multiple sentences on different counts.

It is unclear how this would apply to criticism of Ubolratana. As The Post’s Shibani Mahtani reports, the princess relinquished her royal titles in 1972 when she married an American she met in college (they later divorced). In an Instagram post after her nomination, she described herself as living “as a commoner” without rights and privileges above other Thai citizens.

But given Thailand’s lèse-majesté laws, it’s hard to imagine her opponents or political analysts openly criticizing her. They certainly have good reason to be wary. Some form of lèse-majesté law has been on the books since 1908, though the law was expanded and has been more strictly enforced since a military coup in 1976.

There have been accounts of people arrested on lèse-majesté charges for seemingly minor infractions in recent years: A woman who wore black in 2014 on the birthday of then-King Bhumibol Adulyadej was charged, as was a man who wrote a “sarcastic” Internet post about the revered Thai king’s dog in 2015. Bhumibol died in 2016 and was succeeded by his son, Vajiralongkorn.

Foreigners have been ensnared by the law, too. An American named Joe Gordon was arrested in 2011 for translating excerpts from a book about the king and posting them online (Gordon was pardoned and released the next year). In 2015, a printer in Thailand blocked out an article in a local edition of the New York Times that questioned the monarchy’s future.

Critics of the laws say that their unclear boundaries and broad application leave them open to political abuse. Groups that track lèse-majesté arrests say that they shot up after a military junta seized power in 2014, in part because the new government arrested people for making false claims and other unrelated offenses under the law.

In 2017, the United Nations special rapporteur on the promotion of freedom of opinion and expression, David Kaye, called on Thai authorities to stop using lèse-majesté laws to stifle political speech. “Public figures, including those exercising the highest political authority, may be subject to criticism, and the fact that some forms of expression are considered to be insulting to a public figure is not sufficient to justify restrictions or penalties,” Kaye said.

By some accounts, use of the laws has declined in the last couple of years. But the prospect of a fraught election in March could raise real questions about its use. Ubolratana was nominated for her position by the Thai Raksa Chart Party of Thaksin Shinawatra, a former prime minister who was ousted by a coup a decade ago. Critics have accused Thaksin’s movement of being anti-monarchist, and some of his “red shirt” followers served prison time for lèse-majesté.

The Thai royal palace put out a statement Friday saying that Ubolratana’s nomination was “extremely inappropriate.” It is not clear how King Vajiralongkorn would react further if his sister were to run, but there have been some signs in the past that even Thai royals had their doubts about lèse-majesté laws.

“When you say the king can do no wrong, it is wrong. We should not say that,” King Bhumibol said in 2005. He added that criticism allowed him to make better decisions and that jailing people for criticizing him put him in an awkward position internationally.