Cambodia’s king has officially appointed army chief Hun Manet to succeed his father Hun Sen as the nation’s leader later this month after their party sealed victory in a one-sided election last month.

The royal decree signed by King Norodom Sihamoni means the 45-year-old Hun Manet is officially the incoming Prime Minister and will take office on August 22 when the new National Assembly adopts the new cabinet.

Hun Manet thanked the king for his trust and said in a Telegram post that it was his life’s highest honour to serve the nation and its people.

He added that he was determined to fulfil his duties and promised to keep raising Cambodians’ living standards and the nation’s prestige.

His appointment came after Cambodia’s electoral body on Saturday announced the final results of last month’s election.

The polls that gave Hun Sen’s party a mandate for the next five years were criticised by Western governments and rights groups as neither free nor fair because the main credible opposition party was barred from participating.

Hun Manet won his first seat in parliament in the election, and the handover from his father is part of a larger, generational shift. Many younger legislators are expected to take up ministerial positions, including Hun Sen’s youngest son and others related to older party members.

Many were educated in the West, like Hun Manet, who has a bachelor’s degree from the United States Military Academy at West Point, a master’s degree from New York University and a doctorate from Bristol University, all in economics.

After the royal decree was announced, Hun Sen posted on Telegram and the X social media platform that he was stepping down to give a “chance to the successors to lead”.

Hun Sen, who turned 71 on Saturday, noted that he took office at age 32 as the youngest prime minister in the world at the time.

He added that stepping down as prime minister “is not the end yet” and he would serve in other positions at least until 2033, which would bring him to a half-century in office.

Hun Sen is expected to retain a large amount of control as president of his Cambodian People’s Party and as the Senate president.

“I will still have the ability to serve the interests of the people and help the government oversee the country’s security and public order, as well as joining them in guiding the development of the country,” Hun Sen said on July 26, the day he announced the widely expected succession plan.

Cambodia under Hun Sen has ushered in a free-market economy that raised living standards, but the gap between Cambodia’s rich and poor has widened and land grabs by Hun Sen’s domestic allies and foreign investors are widespread.

After a strong election challenge from the opposition in 2013 that the CPP barely overcame, Hun Sen targeted the opposition’s leaders and the main party was dissolved by Cambodia’s sympathetic courts.

The pattern of crushing any serious opposition followed this year when the main challenger was banned on a technicality before the vote.

The European Union said the election was “conducted in a restricted political and civic space where the opposition, civil society and the media were unable to function effectively without hindrance”.

The US went further, imposing visa restrictions on individuals it considered responsible and pausing foreign assistance programmes.