SINGAPORE (BLOOMBERG) - On his path to becoming Asia's longest-serving leader, Cambodian Prime Minister Hun Sen has mastered the art of fighting for power. When he first took charge of Cambodia as a 33-year-old in 1985, he battled remnants of the Khmer Rouge for control of the South-east Asian nation.

After losing the first election following a United Nations-brokered peace in 1993, he threatened to secede unless he was made co-prime minister. Four years later, a de facto coup put him solely in charge, a position he has kept to this day.

Now 67, Mr Hun Sen is suddenly worried that a group of exiled dissidents might overthrow him by force - a claim that looks hysterical on its face, given many of his main political opponents have been locked up or abroad since he won all of the country's parliamentary seats during a boycotted election last year.

But he has lots of reason to worry. Discontent is building among the country's 16 million people - most of whom have never been alive under another leader - over skyrocketing household debt, resentment at an influx of Chinese investment and a lack of jobs. The European Union is threatening to pull preferential tariffs that could upend the garment sector, the economy's most important industry. And questions over succession are spurring rumours of internal rifts in his ruling Cambodian People's Party.

"There could easily be a popular uprising," said Mr Ou Virak, director of Phnom Penh-based think tank Future Forum and former chairman of the Cambodian Centre for Human Rights.

'PEACEFUL UPRISING'

Mr Hun Sen's opponents see an opportunity to pounce. Long-time opposition leader Sam Rainsy, who has spent the past four years in Paris, has vowed to return to Cambodia to fight for democracy along with others who fled abroad. Mr Hun Sen's government said the efforts amounted to a coup attempt, and he moved the military to the border while warning he'd use "weapons of all kinds" to stop them.

After arriving in Malaysia last weekend, Mr Sam Rainsy told reporters this week he and his colleagues would head to Cambodia "when there is a material, physical possibility to do so".

"I have called on the Cambodian army not to shoot at the people, not to shoot at the civilians, not to shoot at innocent people," Mr Sam Rainsy said. "And Mr Hun Sen is very afraid because he is not sure of the loyalty of the army. The army will stand with the people. The army will not stand with dictators."

Mr Phay Siphan, a Cambodian government spokesman, dismissed talk of an uprising, a mutiny in the army or any internal dissent within the ruling party. "Everything is under control," he said by phone, while also ruling out talks with the opposition. "The government will in no shape or form negotiate with Sam Rainsy."

On Wednesday evening (Nov 13), the government issued a statement appealing to opposition supporters to "stop listening to Sam Rainsy", adding it had fully restored public order after defeating the exiled leader's attempted coup, the AP reported. Mr Sam Rainsy on Tuesday said he could still return to the country "at any time".

Still, Mr Hun Sen has taken at least one step to ease tensions. On Sunday, the government released Mr Kem Sokha, the founder and co-leader of the main opposition Cambodia National Rescue Party, after for more than two years. Another 85 political prisoners are still in custody, according to the UN.

One reason for Mr Kem Sokha's release may be the European Union's looming decision on whether to pull Cambodia's access to a preferential trading scheme due to its deteriorating human rights record. Such a move could decimate its US$5 billion (S$6.8 billion) garment industry and threaten the jobs of about 750,000 Cambodians, some of whom stood with Mr Sam Rainsy during mass rallies in 2013 calling for the prime minister's resignation.

CHINA FACTOR

Mr Hun Sen's move to curtail political and media freedoms over the years has coincided with closer ties with China. As President Xi Jinping's biggest ally in South-east Asia, the Cambodian government has garnered US$7.9 billion in Chinese investment from 2016 to August this year, representing more than a third of all foreign investment, according to the official Xinhua News Agency.

The slew of Chinese property projects and tourists has led to a growing backlash both in the capital Phnom Penh and the once sleepy coastal resort town of Sihanoukville, where more than a dozen new casinos have driven up crime and prostitution. China's stake in an investment zone encompassing 20 per cent of Cambodia's coastline also raised fears in the US that it would become a Chinese naval base, something the government denied.

"Cambodians do not feel good about the Chinese influx and it created insecurity inside the country," said Mr Noan Sereiboth, an influential political blogger and frequent contributor to the youth-centred media group Politikoffee.

Another headache for Mr Hun Sen is growing discontent over mounting public and personal debt. With a median of US$3,370 per loan, Cambodia now has the highest average for small loans in the world, according to a report published in August by local rights groups.

Mostly owed to just nine lenders, the total outstanding amount is equal to roughly a third of the country's entire gross domestic product for 2018, while seven largest microfinance institutions made more than US$130 million in profit in 2017. During last year's election, Mr Hun Sen disavowed connections to microfinance lenders.

QUESTION OF SUCCESSION

Confounding the problem is the question of succession as various factions jostle for power.

Mr Hun Sen's three sons are seen as competing for the top spot, with eldest Hun Manet the odds-on favourite. Educated at West Point and commander of the Royal Cambodian Armed Forces, Mr Hun Manet was elevated last year to the ruling Cambodian People's Party's Standing Committee, a key decision-making body.

Without specifically addressing the opposition's calls for an uprising, Mr Hun Manet took to Facebook on Tuesday implore citizens to enjoy the annual water festival this week.

"What the people do not want is chaos, insecurity, instability and the loss of peace," he wrote. "We must work together to fully protect the peace we have today."

For all the noise, Mr Sam Rainsy's move is "desperate" and has little chance of success, according to Dr Lee Morgenbesser, author of the book Beyond The Facade: Elections Under Authoritarianism In South-east Asia.

"A failure to try (to) re-enter Cambodia would raise significant questions about whether those exiled are the right leaders for Cambodia's pro-democracy movement," he said.