When Prime Minister Hun Sen penned the opinion that China was the “root of all that is evil in Cambodia” in the late 1980s, he probably did not imagine he would come to depend so much on the country.

Yet when Chinese President Xi Jinping touches down in Cambodia at 11am today, he will be arriving as the head of a regime that has become one of the premier’s most important supporters amid increasingly frequent criticism of his authoritarian style.

Far from the China of the 1980s that refused to recognise Hun Sen’s regime and financed the Khmer Rouge resistance fighting to topple it, today’s China has poured billions into the country – often when the regime’s legitimacy has appeared most at threat.

“China has never made a threat to Cambodia, and has never ordered Cambodia to do something,” Hun Sen warned the rest of the world during a speech earlier this year, after Europe’s parliament threatened to cut aid if he did not end a wave of repression.

“Don’t scare me,” he warned. “Don’t threaten me. Don’t threaten Cambodia by cutting off aid.”

China’s largesse has been rewarded by the premier, who has used the country’s veto in the ASEAN bloc to prevent it from issuing statements against Beijing’s aggressive South China Sea claims – and inevitably opened Cambodia up to claims of becoming a client state.

But the seemingly easy fit between the CPP and China’s authoritarian government over the past few years was a long time coming, with the party’s wholesale embrace of its former enemy only arriving two decades after relations were normalised in 1991.

“A number of factors are at play here,” said Lee Morgenbesser, who researches elections under authoritarian regimes at Australia’s Griffith University. “First, the CPP has historically been more closely aligned with the Communist Party of Vietnam.”

“The existence of this longstanding bilateral partnership would naturally take some time to be edged out by the Chinese Communist Party, who initially represented a more risky and less rewarding alternative,” he said.

“Second, the riches on offer from China are far more enticing now than any time in the 1990s or 2000s.”

Most recently, and less than a week after Cambodia nixed another ASEAN statement, China pledged $600 million in aid until 2018, the year of the next national election, when the CNRP hopes to put an end to the CPP’s almost four-decade grip on the country.

CPP spokesman Sok Eysan said the government appreciated the billions Beijing had provided since the ruling party properly mended its relationship after the bloody 1997 factional fighting that destroyed the power of China’s preferred partner, Funcinpec.

“We welcome all funds from Chinese to develop and build the country,” Eysan said, while also denying that China’s long support for the Khmer Rouge, which only ended in 1991, should still be remembered.

“We have not thought about that, because the Khmer Rouge regime has ended, and therefore there is no need to remind [people] about that,” he said. “This bitter old history should not be brought up.”

While the CPP and Hun Sen himself justify much of their rule by reminding Cambodians of their part in overthrowing the Khmer Rouge, the Chinese president has been less than keen to remember his country’s support for the guerrillas long after their regime was toppled in 1979.

An essay that he penned on the front page of yesterday’s CPP-aligned Rasmei Kampuchea Daily took a much more positive line about Chinese-Cambodian relations than Hun Sen’s missive of 30 years ago, avoiding any mention of the Khmer Rouge. Instead, Xi’s essay focussed on Cambodia’s steadfast support for China on its “core issues”, as the rest of the world shuns the country’s recalcitrant stand on its disputed territorial claims to South China Sea.

“We cannot forget that amid the rise of a new China, which has been censured and considered as an enemy by many countries, Cambodia has led the way in establishing good relations with China,” Xi wrote.

“China and Cambodia are good and honest friends. On issues related to core interests . . . the two countries come together to help each other.”

And while Cambodia’s contributions to supporting China’s “core interests” in the South China Sea are apparent enough, for Hun Sen it has not only been the sheer volume of cash on offer that has made China such an appealing international friend.

“Perhaps more importantly, it now has a 20-year track record of steady support for the CPP,” said John Ciorciari, a Cambodia scholar at the University of Michigan’s Gerald R Ford School of Public Policy, explaining that loyalty had currency with the CPP.

“Since the 1990s, when CPP leaders patched fences with China, the relationship has shifted from one marked by mistrust to one in which China is seen as the CPP’s most reliable foreign friend,” he said. “Cambodian domestic politics also play a role. As Hun Sen looks toward elections and fears further erosion of popular support, China provides the most credible external backstop to his illiberal regime.”

CNRP spokesman Yim Sovann yesterday declined to comment on whether the opposition was concerned by the CPP’s dramatic turn towards an authoritarian government like China and its seemingly growing disinterest in trying to please Western nations.

“The CNRP’s position is to maintain relationships with all countries in the world that give benefits to our nation. We think relations with all of the world are beneficial,” Sovann said. “We do not want to make comments on what the government does with China.

“When the CNRP is in power, we have our own policies to build up relationships with all countries, and we do not regard any country as an enemy. We need to have mutual cooperation with everyone.”

However, with many questioning the CPP’s interest in holding free elections in July 2018, the opposition will have to hope Hun Sen still places some value in the democratic legitimacy conferred by pleasing the West, rather than cosying up further with Xi.

“The CPP is still concerned about its relations with the US and EU,” said Ciorciari. “That said, Western donors clearly have less clout in Cambodia than they did in the past, especially as Beijing offers the CPP an alternative source of support.”

Additional reporting by Mech Dara