“Whether it’s the courts or the tax department or new legislation, all these mechanisms are being used by the government to crack down on its critics,” she said.

Also facing a tight deadline is The Cambodia Daily, an independent newspaper that has served as a training ground for local reporters and budding foreign correspondents alike.

The newspaper has been issued a tax bill of more than $6 million, which it contests. On Tuesday, while at an environmental event in the capital, Phnom Penh, Mr. Hun Sen implied that the newspaper, which was founded by an American journalist, was a “thief” and said it needed to “pack up and leave” if it failed to pay back taxes. The deadline to pay is Sept. 4.

The action has alarmed free-speech advocates, who say the paper has aggressively pursued worthwhile topics.

“The Cambodia Daily has tried to apply international standards of news writing in Cambodia, and it has aggressively covered sensitive issues, like corruption, land-grabbing and illegal logging,” said Moeun Chhean Nariddh, director of the Cambodia Institute of Media Studies. “But unfortunately Cambodian democracy is very young. Press freedom is still fragile.”

At least a dozen Cambodian journalists have been murdered since the early 1990s. Human rights activists have been fatally shot in broad daylight. In recent days, other news media organizations that have aired views critical of the government have been threatened.

The Cambodian Ministry of Economy and Finance has also raised questions about the legal and tax status of Radio Free Asia and Voice of America, which both get United States government funding. Local radio stations supportive of the opposition have been silenced.

“Every day that we get to put out a newspaper is a good day for us,” said Jodie DeJonge, the editor in chief of The Cambodia Daily, which has clashed for decades with government officials and tycoons over its investigative pieces. “There is still a free press in Cambodia, and we are going to rely on that until they come and put yellow tape around the building.”