The eldest son of Cambodia's long-standing ruler has received official approval to become the country's next prime minister, marking a formal transition of power.

Cambodia's king issued a decree on Monday declaring that Hun Manet will succeed his father, Hun Sen, who has held power for 38 years. Hun Sen's decision to step down came shortly after the July 23 election, which was criticized for lacking democratic fairness due to the exclusion of the main opposition.

Hun Manet, aged 45 and formerly the commander of the Royal Cambodian Army, has been groomed for leadership for some time. His appointment, though requiring confirmation by parliament on August 22, is expected to be easily approved given the majority control held by Hun Sen's Cambodian People's Party in the National Assembly.

This succession follows a dynastic plan that Hun Sen had indicated for several years. Hun Manet's upcoming cabinet is anticipated to include younger members, as many of the individuals who rose to prominence alongside Hun Sen during the Khmer Rouge revolution and subsequent civil war have retired, often passing their roles to their own children.

The transition process had been hinted at since 2021, but the specific timing remained uncertain until July.

However, Hun Sen announced that he would step down just three days after the election. He is one of the world's longest-serving leaders, having ruled the South East Asian nation of 16 million people for nearly four decades.

He said at the time he was resigning to ensure stability in Cambodia.

Hun Sen will however retain leadership of the ruling Cambodian People's Party - a position political analysts say still gives him ultimate control.

His rule has become increasingly authoritarian since coming to power in 1985, and he has silenced opponents by either jailing or exiling them.

On the weekend, in addition to marking his 71st birthday, Hun Sen confirmed the party's landslide victory in the July election - polls which the US, EU and other Western nations have said was neither free nor fair.

Hun Manet celebrated Saturday's election result by posting a photo to Instagram showing his son presenting a bouquet of flowers to Hun Sen with the caption: "Happy birthday to respected and beloved father."

The outgoing leader on Saturday also confirmed Hun Manet's election as an MP for Phnom Penh, removing the remaining procedural obstacle for his ascent to power.

With all meaningful opposition shut down in Cambodia in recent years, Hun Manet will face few threats from outside the ruling party. But maintaining the complex web of alliances his father built with other powerful and wealthy families will be a challenge.

Hun Sen dispensed political and business privileges to potential rivals to keep them happy, and the economy growing. But he also saddled Cambodia with incendiary levels of corruption and inequality which could store up trouble for his inexperienced son.

Compared to his father, some have speculated that Hun Manet, who attended US military academy West Point and the University of Bristol, could lead a less repressive regime and be more receptive to Western calls on human rights.

However, there is little evidence to suggest he will be more open. Hun Sen has also made it clear that he will continue to wield enormous influence over the running of the country for at least another 10 years.

In a telegram post on Monday, Hun Sen wrote of his son's appointment: "It is not the end yet. I will continue serving in other positions for at least until 2033."

Congrats to him