Hun Sen has publicly backed Hun Manet to lead the kingdom in the future.

Hun Manet, who is commander of the army, received the four-star rank at a ceremony attended by more than 1,000 senior military officials.

Defence minister Tea Banh, who presided over the ceremony, said Hun Manet's promotion reflected his efforts "to serve the nation, military and Cambodian people".

Hun Manet -- who was educated in Britain and the United States -- has been officially backed by the ruling party as a future prime minister, and has been active on social media in recent months to increase his public profile.

The 45-year-old has also had more diplomatic meetings with senior political figures than before, according to the Lowy Institute's Asia Power Index.

In 2022 he met 10 world leaders, deputy leaders and foreign ministers, compared with only two in 2019, the institute said.

He will run for a parliamentary seat when Cambodia goes to the polls in July this year, according to a party document seen by AFP.

Hun Sen, who has ruled the country for 38 years, has repeatedly hinted at stepping down but has said he will run for office again in the coming election.

The prime minister, who has wound back democratic freedoms and used the courts to stifle opposition, frequently characterises his children's achievements as the product of education and training, and rejects claims of nepotism.

At the last general election in 2018, Hun Sen's party won every seat in parliament after the Supreme Court dissolved the main opposition, the Cambodia National Rescue Party (CNRP) a year before.

A court last month found Kem Sokha, a co-founder of the CNRP, guilty of conspiring with foreign entities to overthrow Hun Sen's government.

He was sentenced to 27 years in prison and immediately placed under house arrest.

Scores of opposition figures were convicted of treason last year and Hun Sen ordered the shutdown of one of the country's few remaining local independent media outlets in February, over a report about Hun Manet.