Thailand's royal family is shielded from scrutiny and criticism by a strict lese-majeste law, under which defaming, insulting or threatening the king, the queen, the heir-apparent or the regent can be punished with up to 15 years in prison.
Openly opposing the crown was unthinkable under the previous monarch, King Bhumibol, who enjoyed much greater popularity than his son and successor, King Vajiralongkorn.
Although pro-democracy activists insist they merely want to reform the monarchy,Thai royalists say they activists want to overthrow the institution.
Two days later, Prime Minister Prayuth threatened to apply Section 112 of the Thai Criminal Code, which punishes lese-majeste, in full force.
"It is necessary for the government and security agencies to enhance our measures by enforcing all the pertaining laws against protesters who violate the law or infringe on the rights and freedoms of other citizens," he said.
Undeterred by the government's threats, demonstrators gathered on November 25 around the Siam Commercial Bank headquarters — in which the king is a major shareholder — to demand greater transparency of the monarch's finances.
The rally was held after police had summoned 12 protest leaders for questioning over royal defamation allegations — the first formal application of the lese-majeste law in more than two years.
'Not afraid' of lese-majeste law
"I am not afraid. I understand that invoking this law is the government's plan to suppress us," Patsaravalee Tanakitvibulpon, a 25-year-old engineering student and prominent activist accused of defaming the monarchy, told DW.
Patsaravalee is one of the leading protest figures calling for reforms to the monarchy. She is facing charges of royal defamation.
Speaking about the law, Patsaravalee said, "I think it is illegitimate to enforce this law… to obstruct people's freedom to speak the truth even though there are now many accusations about royal involvement in politics."
Critics say law is unclear
Since the 2014 coup led by Prayuth — a loyal monarchist who stayed on as prime minister following the general election in March last year — at least 98 persons were charged with lese-majeste, according to human rights organization iLaw.
Critics have argued for years that the law's unclear boundaries give authorities leeway to interpret the rule broadly and leave room for political abuse.
While has not been invoked in recent years, other vaguely worded legislation, such as the Computer Crime Act and sedition law, have been serving as additional legal avenues for the government to crack down on dissidents.
In June this year, Prayuth told the country that the king, on compassionate grounds, had instructed the government not to enforce Article 112 for persecutions.
But for protesters like Patsaravalee, the revival of the lese-majeste law, despite this promise, shows that authorities are willing to use every political weapon to curb the pro-democracy movement.
"The government is always ready to use every means at their disposal to obstruct the freedom of the people and retain their grip on power," she said.
'Inconsistent' with international law
The law against royal defamation— which the United Nations has said is "inconsistent with international law and should be repealed" — has been in place since the early 1900s.
It has also been embodied in Thailand's constitutions, which state: "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."
Thai monarchs had absolute power for hundreds of years, until a 1932 revolution ushered in a constitutional monarchy.
But despite losing absolute power, the royal family has retained an influential role and powerful supporters, as traditionalists still view the monarchy as a sacred institution.
"This kind of law was already repealed in other countries where the king is head of state. Even in those where this law still exists, the punishment is not harsh, whereas its use in Thailand has increased in frequency and each time, it is used for political gains," Patsaravalee told DW.