BANGKOK — His offense was syncopated. And it rhymed.
Dechathorn Bamrungmuang, a member of the Thai collective Rap Against Dictatorship, was arrested on Thursday on charges of sedition, human rights lawyers said, part of a mounting crackdown by a government seemingly allergic to dissent.
A day earlier, the authorities took into custody for the second time a lawyer who had publicly called for the Thai monarchy’s powers to be reined in. At least six pro-democracy activists were also arrested on Wednesday and Thursday on charges of sedition, a crime that can carry a seven-year prison sentence, the organization Thai Lawyers for Human Rights said. Another rapper was taken in, too. Yet more student activists were served with papers that appeared to indicate they could be imminently detained.
“The United Nations and concerned governments should speak out publicly against the rolling political repression in Thailand,” Brad Adams, Asia director at Human Rights Watch, said in a statement. “Thai youth are increasingly demanding real progress toward democracy and the rule of law so they can freely express their visions for the future of the country.”
The legal actions followed weeks of protests by students that culminated on Sunday in the largest street rally in Thailand since a military coup six years ago. Because of a state of emergency imposed to control the coronavirus, the protests were technically illegal. But that did not stop more than 10,000 people from gathering at Democracy Monument in Bangkok.
On Wednesday, hundreds of students, who have been protesting school rules like mandatory haircuts and the tradition of prostrating themselves to teachers, gathered at the Education Ministry in Bangkok, calling for an end to the regimented strictures of Thai society. They raised three fingers in the air, a symbol of defiance drawn from the “Hunger Games” films that was once banned by the junta behind the 2014 coup.
Thailand has held elections over the decades, but meddling by the military has regularly upended the people’s vote, with a dozen successful coups since absolute monarchy was abolished in 1932. A former army chief who led the last coup, Prayuth Chan-ocha, remains prime minister. Three other retired generals hold cabinet positions.
Mr. Prayuth has said that he is willing to listen to the students. He has also joked that he would like to execute journalists who veer from the truth and assailed those who have called for more accountability over the monarchy.
The junta leaders said protecting the palace was a key reason for their putsch, and the current government, which took power last year after elections that independent observers said were flawed, often wraps its policies in a royal mantle.
King Maha Vajiralongkorn Bodindradebayavarangkun is present in Thailand for only days at a time, living most of the year in Europe. Since his father died in 2016, he has consolidated his authority, taking control of royal coffers and army units that traditionally add their firepower to coups.
Thailand is bound by strict laws that criminalize criticism of the monarchy, potentially landing offenders in jail for up to 15 years. In addition to the lèse-majesté laws, the government has also imprisoned people for contravening sedition and computer crimes laws. Hundreds of people have been funneled through so-called attitude adjustment camps that are run out of military compounds. Dissidents have disappeared, too, with some of their bodies turning up mutilated.
The transgression of Mr. Dechathorn, who goes by the rap name Hockhacker, appears to have been a musical performance at a pro-democracy rally, according to the group of rights lawyers.
In 2018, Rap Against Dictatorship, the Thai musical collective, drew millions of hits for a widely shared video for a song called “What My Country Has Got.” The song referenced a student massacre and called Mr. Prayuth’s government to account for leading a “country that makes fake promises like loading bullets, creates a regime and orders us to love it.”
Another song, released this year, took on student hazing. The collective was awarded the Vaclav Havel Prize for Creative Dissent in 2019.
Sirin Mungcharoen, a pro-democracy activist from Chulalongkorn University in Bangkok, said she received a police summons on Wednesday related to a protest in Bangkok on July 18. Ms. Sirin said that she had attended that student rally, but was not an organizer.
“It’s a way to create fear,” Ms. Sirin said, adding, “I will keep fighting.”
Muktita Suhartono contributed reporting from Phuket, Thailand.