Hun Manet shows his finger after casting his vote at a polling station in Phnom Penh in July 2023
Hun Manet shows his finger after casting his vote at a polling station in Phnom Penh in July 2023 AFP

Cambodia's king on Monday will appoint Hun Manet the country's new leader after his father Hun Sen calls time on nearly four decades of hardline rule.

Days after a landslide victory in July's election, Hun Sen -- one of the world's longest-serving leaders -- announced he was stepping down as prime minister and handing power to his eldest son.

The polls were widely decried as a sham after the opposition challenger Candlelight Party was barred from running over a technicality, with the ruling Cambodian People's Party (CPP) winning all but five seats in the 125-member lower house.

On Monday, following a request from Hun Sen, King Norodom Sihamoni is set to issue a royal decree making four-star general Hun Manet the prime minister.

However, to officially become the country's new leader the 45-year-old and his new cabinet must win a confidence vote in parliament set for August 22.

The incoming government will usher in a crop of young ministers -- with some taking posts vacated by their fathers.

While insisting he would not interfere with his son's rule, Hun Sen has promised Cambodians he will continue to dominate the country's politics.

Having come to power in 1985, he helped modernise a country devastated by civil war and genocide, although critics say his rule has also been marked by environmental destruction, entrenched graft, and the elimination of nearly all political rivals.

The United States, United Nations, and the European Union condemned last month's polls as neither free nor fair.

Hun Sen rejected those allegations and said his handover, a dynastic succession compared by some critics to North Korea, was being done to maintain peace and avoid "bloodshed" should he die in office.

He also warned that should Hun Manet's life be seriously endangered, he would return as PM.

While groomed for the position for years, the eldest son of Cambodia's iron-fisted ruler remains untested in the political arena, analysts say.

And there are few expectations Hun Manet will chart a more liberal path than his father, despite being educated in England and the United States.

A member of the ruling party's powerful permanent committee, he has been the Royal Cambodian Army's commander since 2018.

Hun Manet has also met some world leaders including President Xi Jinping of China, Cambodia's main ally and a significant benefactor.

After stepping down, Hun Sen will become president of the Senate early next year and acting head of state when the king is overseas.