Phimchanok was charged with royal defamation for a post on her Facebook profile page saying “The government sucks. The institution also sucks.” Pol Col Nopparit Kantha, the superintendent of the provincial investigation department in Chiang Mai, filed charges against her on order of the Chiang Mai regional police working group on national security. Assuming the term “institution” was a reference to the monarchy, the police accused her of royal defamation.

Phimchanok was arrested on 18 March 2022 by a unit of around 15 officers and taken from Bangkok to Chiang Mai. The warrant was issued by the Chiang Mai Provincial Court. She never received a summons before being arrested.

Although Phimchanok’s lawyer requested bail during the inquiry process, the police said that a bail request could only be filed after she had been taken to court for temporary detention. Although the Chiang Mai Provincial Court granted her bail, she was not released until 11.40 on 19 March 2022. This caused her to miss her TCAS examinations, required for university entrance. Thereafter, she was also required to report to the court in Chiang Mai every 12 days, although she lives in Bangkok.

In court, Phimchanok testified that she posted the message but was referring to an educational institution, not the monarchy. She added that even if others think that it refers to the monarchy, it did not constitute royal defamation as the defamation law protects specific members of the royal family, not the royal institution.

On Wednesday (6 September), the Chiang Mai Provincial Court found her guilty of royal defamation. Thai Lawyers for Human Rights (TLHR) said that the court cited prosecution witness testimonies saying that Phimchanok has previously been advocating for monarchy reform, making it probable that her post referred to the monarchy. The court also ruled that the royal defamation law covers the royal institution as well as the King, Queen, and Heir Apparent, members of the royal family specifically listed in the text of the law.

The court sentenced Phimchanok to 3 years in prison, but reduced her sentence to 2 years because she gave useful testimony. She was later granted bail using a 150,000-baht security and will be appealing her sentence.

TLHR noted that interpretation of the royal defamation law tends to vary from court to court. On 21 August 2023, the Chiang Mai District Court dismissed one count of royal defamation charge filed against student activist Thanathorn Vitayabenjang on the grounds that the statement he read during the protest in front of the Provincial Police Region 5 headquarters mention the monarchy but not specific members of the royal family. However, he was found guilty of another count of defamation for a speech given at the Three Kings Monument, which mentioned the King.