Sihamoni, 72, shared his diagnosis earlier this month, saying he would stay in China for prolonged treatment.

The monarch had surgery at a Beijing hospital on Monday morning, the Royal Palace in Phnom Penh said in a statement.

Chinese doctors were requiring Sihamoni to stay in hospital for health monitoring, it added.

The king said earlier that doctors had prescribed hospitalisation of up to two months for treatment.

In a social media post, influential former leader Hun Sen, who visited Sihamoni in Beijing along with his eldest son, Prime Minister Hun Manet, thanked the “excellent doctors who performed the successful and safe surgery for the king”.

“The health of the king is the health of the whole nation,” Hun Sen added, saying he would return to Cambodia if the king’s health improved.

Hun Sen ruled Cambodia for nearly four decades and handed power to Hun Manet in 2023.

The king departed for Beijing for health checks over a month ago.

A lifelong bachelor who speaks Khmer, French, Czech and English, Sihamoni spent most of his adult life abroad pursuing a career in the arts before taking the throne in 2004.

He took over the role after his father, King Norodom Sihanouk, abdicated following his own cancer treatment in Beijing.