Chinese officials are planning to put Tashi Wangchuk, who advocates broader Tibetan language education, on trial next week for “inciting separatism,” a charge that could result in a sentence of up to 15 years in prison, according to his lawyers.

Mr. Tashi, 32, has been detained for nearly two years in and around the town of Yushu, on the Tibetan plateau in the far west of China. He is among the most prominent political prisoners in China. The police took him from his home in January 2016, two months after he appeared in a New York Times video and article about Tibetan language education. Mr. Tashi had also written blog posts on the subject.

International human rights supporters and Tibet advocacy groups denounced the upcoming trial after Liang Xiaojun, one of Mr. Tashi’s lawyers, wrote online this week that officials at the Yushu Intermediate Court in Qinghai Province had scheduled Mr. Tashi to appear in court on Thursday. One rights advocate, Michael Caster, said on Twitter that the case was “a travesty.”

Communist Party officials generally decide the outcome of political trials in China; the accused is almost always convicted and sentenced to prison.

Because of the prominence of Mr. Tashi’s case, any sentencing would lead to further international condemnation of China’s record of rights abuses. Human Rights Watch, Amnesty International, PEN America and the United States Embassy in Beijing have all publicly criticized the Chinese government over the case.

In December 2016, the United States ambassador to China at the time, Max Baucus, released a long statement on political prisoners that noted Mr. Tashi was “in jail for his peaceful advocacy of Tibetan language education.” Human Rights Watch called on China to drop the charge against Mr. Tashi.

Ethnic minority issues are among the most sensitive in China. The police in Yushu were especially angry at Mr. Tashi over his interviews for the Times video on the Tibetan language, Mr. Liang said in an earlier interview. Yet Mr. Tashi told Times journalists that he did not support Tibetan independence or separatism and was instead merely pushing for the Tibetan language to be properly taught in local schools, which prioritize Chinese language education, and for Tibetan to be used in government offices.

Mr. Tashi had insisted on doing on-the-record interviews, saying that only those would be meaningful for viewers and readers. The Times video, produced by Jonah M. Kessel, showed Mr. Tashi traveling to Beijing to try to bring a lawsuit against Yushu officials to compel them to expand Tibetan language education. The video also showed Mr. Tashi trying to get Chinese state news organizations to report on his mission.

Mr. Tashi’s plight has become a rallying point for Tibetans abroad. In July, Tibet advocates outside Tibet and China gave Mr. Tashi the Tenzin Delek Rinpoche Medal of Courage, an award whose judging panel also included representatives of Human Rights Watch and the British branch of Amnesty International. The award was “in recognition of his courage and dedication to promoting Tibetan human rights and justice for the Tibetan people,” the judges said in a statement.

Mr. Tashi’s case has taken unexpected turns. In March 2016, police officials said in a document that they were investigating Mr. Tashi for inciting separatism. After getting material from the police, prosecutors then handed the case to the court to seek a formal indictment and trial against Mr. Tashi. But then they asked the court to give the case back to them for further investigation. Lin Qilei, one of Mr. Tashi’s lawyers, said at the time that this was “very rare.”

One year later, the court appears ready to hold the trial. Mr. Lin said that he planned to fly to Yushu on Tuesday.

Mr. Tashi ran a shop in central Yushu, called Gyegu in Tibetan, and sold goods from the region to buyers across China on Taobao, an online platform run by Alibaba, the e-commerce giant. In 2014, Alibaba chose Mr. Tashi to be featured in a video for the company’s investor roadshow before an initial public offering.

Many Tibetans resent rule by the Communist Party. In 2008, Chinese security forces suppressed a widespread Tibetan uprising. Since 2009, at least 160 Tibetans have self-immolated in what appear to be acts of protest against the party.