In his own bunker across the city, Prince Norodom Ranariddh, co-prime minister and Hun Sen's avowed rival, surrounds himself with fewer gun- toting bodyguards.
Both men are drilling their troops and priming their tanks as the country edges towards renewed civil war.
After clashes on Tuesday night between the two prime ministerial bodyguard units, troops from rival army factions have been deployed on the streets of the capital, Phnom Penh, in anticipation of further violence.
Cambodia's two vying leaders, divided over most issues, are locked in a dangerous stand-off over plans to induct defecting Khmer Rouge guerrillas into the government army, and to allow the reviled leaders of the movement, with the exception of Pol Pot, back into politics.
Hun Sen has opposed this, and has delivered an angry ultimatum to Prince Ranariddh, warning him that he must choose between staying in power and embracing the Khmer Rouge.
A former Khmer Rouge commander, who collaborated with Vietnamese forces to oust the genocidal movement in 1979, Hun Sen remains a bete noire to members of the group, frequently lambasted on clandestine guerrilla radio as a "Hanoi puppet" or a "piece of excrement". Understandably, he is uncomfortable with the prospect of joining hands with his former Khmer Rouge colleagues.
Moreover, an influx of heavily armed, well-trained fighters into army ranks loyal to Prince Ranariddh would weaken Hun Sen's hitherto unchallenged military superiority.
"It is ironic that the fall of the hated Khmer Rouge ... which should be a uniting factor for the country, is proving to be a divisive one," said Ker Munthit, a veteran analyst based in Phnom Penh. "We are now in an extremely dangerous time in Cambodia
Since the 1993 elections, in which Prince Ranariddh's Funcinpec party was returned to power, Cambodia has been in political limbo. Hun Sen, wielding considerable military muscle, has threatened to abandon the 1991 United Nations peace deal and revert - along with the Khmer Rouge - to civil war.
To appease his Cambodian People's Party (CCP), Hun Sen was offered a co-premiership, resulting in an uneasy coalition and intense rivalry.
In recent months, tension has fuelled political violence as both men jostle for advantage in the run-up to general elections next year, after which only one prime minister can assume office.