BANGKOK — Theary Seng, a Cambodian American lawyer and a human rights activist, was sentenced to six years in prison on Tuesday as part of Cambodia’s wide-ranging crackdown on opponents of the nation’s prime minister, Hun Sen.
Ms. Theary Seng — a refugee who escaped Cambodia’s killing fields and who had returned from the United States to help build democracy — was convicted of conspiracy to commit treason, along with dozens of other critics and opposition politicians.
Choung Chou Ngy, her lawyer, said he planned to appeal her conviction. He said that those who had received five-year terms had their sentences suspended but that the other defendants with five to eight years would face prison time.
All of them were victims of a concerted campaign by Mr. Hun Sen to eliminate the last traces of resistance to what has in effect become his one-man rule. The main opposition party, to which many of the defendants belonged, was dissolved by court order in 2017, prompting many of its members to flee abroad.
Since then, top leaders of the party, the Cambodia National Rescue Party, have been harried with court cases, with some convicted in absentia more than once on separate charges.
In March, 19 members of the party, including a half-dozen leaders in exile, were convicted on charges of “incitement” and “conspiracy,” and many were sentenced in absentia to prison terms.
At that time, Phil Robertson, the deputy Asia director of Human Rights Watch, called the trials “a witch hunt” and said, “Cambodia’s politicized courts have facilitated Prime Minister Hun Sen’s effort to destroy the last remnants of democratic freedoms and civil and political rights in the country.”
Mr. Hun Sen’s party, the Cambodian People’s Party, now holds all of the seats in the National Assembly. The prime minister, 69, recently announced that he would eventually hand over leadership of the country to his son Hun Manet, a lieutenant general.
Mr. Hun Sen was the prime minister in a Vietnam-installed Communist government after the Vietnamese ousted the Khmer Rouge, which had caused the deaths of around two million people in the late 1970s.
After their ouster, the Khmer Rouge waged a jungle insurgency until the United Nations brokered a deal and set up a Western-style democracy with political freedoms and human rights guarantees.
Mr. Hun Sen remained in power, sharing it for a time with a co-prime minister, Norodom Ranariddh, after a U.N.-sponsored election.
It was in this context that Ms. Theary Seng — who had survived the killing fields of the Khmer Rouge, fled to America and earned a law degree — returned to Cambodia in 2004 as part of a struggling human rights movement.
In an interview last year, she said she had returned to help “stem Cambodia’s complete plunge into autocracy.” Looking back, she said, “There was such high hope when I entered civil society.”
But Mr. Hun Sen was already moving step by step to gather power and eliminate opposition through imprisonment, exile, payoffs, electoral manipulation, assassination and coup.
As human rights defenders fled or were arrested, Ms. Theary Seng remained one of the most insistent opponents of the government.
Ms. Theary Seng retained her United States citizenship but said she was determined not to flee, though she could have. The State Department criticized the charges against her and the other defendants as “baseless,” and the United States Embassy said it was monitoring the trial.
Since being indicted along with dozens of others in November 2020, and with the government-controlled news media and other avenues of expression closed to her, she has resorted to flamboyant displays to attract attention.
On the day of her sentencing, she was wearing the latest in a series of extravagant costumes, this time dressed as Lady Liberty with her face painted green and with a spiked crown and green gown, which she was still wearing when police officers bundled her into a van.