For 30 years Aun Pheap reported on corruption, human rights abuses, elections and political scandals for every major newspaper in Cambodia, a job he felt he was born to do. Now, like so many journalists who worked in Cambodia’s once free press, he is in exile, branded an enemy of the state.

For Pheap, formerly a reporter at the Cambodia Daily, which shut down last year, “this is the worst situation for the press and for journalists I have seen in my whole 30-year career”. And it has worsened further this week, with the sale of the Phnom Penh Post, seen as the last bastion of the free press in Cambodia, to the owner of a Malaysian PR company who has links to the regime of the Cambodian prime minister, Hun Sen.

The development was described by Phil Robertson, the deputy Asia director of Human Rights Watch, as “a staggering blow to press freedom in Cambodia”.

In less than a year, Cambodia has gone from having the freest press in the region to being one of the most repressive and dangerous places to be a journalist. In the 2018 Reporters Without Borders press freedom indexpublished last month, Cambodia dropped 10 places from 132 to 142, and the country’s independent press was described as being “in ruins”. This was echoed by the Cambodian Centre for Independent Media, which recently concluded that the “facade” of free press in Cambodia had collapsed entirely, with almost half of journalists reporting intimidation.

Hun Sen’s all-out war on the independent media began in early 2017, as journalists found themselves followed and harassed by secret police and controversial commentators were arrested. Then, in September, the Cambodia Daily – which had been accused of a pro-opposition stance – was forced to close over a disputed $6.3m (£4.6m) tax bill.

This was swiftly followed by the shutting down of the Phnom Penh office of Radio Free Asia (RFA), which produced some of the most popularly consumed reporting on human rights violations and illegal government activity. Overall, 32 radio station across 20 provinces that broadcast reports critical of the government were forced to close last year.

And then on Saturday, the Australian publisher of the the Phnom Penh Post, Bill Clough, confirmed he had sold the newspaper to a Malaysian businessman, Sivakumar G, who owns Asia PR. While Clough claimed the Post’s editorial independence would remain intact, Asia PR’s previous projects include “Cambodia and Hun Sen’s entry into the government seat”.

The timing of the sale, coinciding with the Post settling its much-publicised $3.2m tax bill with the government, has also raised alarm.

Journalists in the country talk of the “complete obliteration” of its independent press. Speaking to the Guardian from Washington DC, where he is seeking political asylum, Pheap voiced his sorrow. “Any journalist who writes the real situation of Cambodia, anything that the government doesn’t like, then they will do everything to intimidate or prosecute us, and make sure we do not feel safe in our own country,” he said. “Because of this I have lost everything.”

Not long after the Cambodia Daily closed, Pheap found himself charged in court with “inciting crime”, relating to an incident where he allegedly encouraged people to support the opposition while reporting on the elections in Ratanakiri province last May. In early October he was forced to flee to Thailand to avoid a jail sentence, leaving behind his family.

Pheap says the accusations are entirely false and politically motivated, and in fact relate to his reporting on the government’s involvement in the illegal logging trade. “We told the truth but made the local authorities look bad,” he said. “This is the real reason we are being punished.”

The climate of fear for journalists in Cambodia worsened in November when two former RFA reporters, Uon Chhin and Yeang Sothearin, were arrested and accused of “illegally collecting information for a foreign source”. They deny all charges but are still in jail awaiting trial. An Australian journalist has also been jailed on an espionage charge.

The reason for Hun Sen’s rapid clampdown on the press appears directly linked to the upcoming elections on 29 July, and a suspicion the opposition were gaining too much support – an unpalatable prospect for a leader who has held on to power since 1985. Critics say that in a two-pronged attack on democracy in Cambodia, his solution was to demolish the independent press that gave a platform to criticism, and then dissolve the opposition, the Cambodia National Rescue party (CNRP), in October. Kem Sokha, the leader of the CNRP, is in jail charged with treason.

“It’s a rapidly deteriorating situation,” said Shawn Crispin of the Asia branch of the Committee to Protect Journalists. “It’s clear that they now see a free media as a potential threat to their continued stay in power and this clampdown was pre-emptively timed for these upcoming elections. The cold hard fact is that there is a lot less news now coming out of Cambodia – they have been able to pull the curtain down on what was a very free media very quickly.”

Crispin added that journalists no longer knew where the line was when it came to reporting on the government, and uncertainty over what could lead to charges of treason meant self-censorship had become the norm in the press.

While many Cambodia Daily and RFA reporters fled the country after the closures some stayed and say they live in fear or are subject to daily harassment from the authorities. A former RFA journalist still living in Cambodia, who preferred to remain anonymous to protect his family’s safety, said he had not been able to sleep “for months”. In the months building up to its closure, RFA journalists knew they were under attack from the government – the office installed bulletproof glass and hard drives were taken home at night – but he never expected the station to be shut down.

“They are out for revenge for Radio Free Asia journalists because we reported the truth, and now there is no law here to protect us,” he said. “I don’t think you can say there is fully neutral or independent media left in Cambodia any more, because Hun Sen got scared he will lose the election. Even if you are brave enough to report the truth, editors will not publish it.”

The biggest question is whether after a victory in July’s elections, Hun Sen will loosen restrictions on the media, though most are not optimistic. Ed Legaspi of the Southeast Asian Press Alliance said he felt the worst had been done.

“The ruling party doesn’t need to do anything further to intimidate the media,” he added. “Unfortunately they have been very effective. Right now in Cambodia the government has the upper hand.”