Former Cambodian king Norodom Sihanouk, who abdicated in favour of his son Sihamoni last year, has called for official portraits of himself and his wife to be removed from public display.

Sihanouk, who is currently in Beijing for medical treatment, asked the government and private citizens to take down images of himself and former queen Monineath from schools and public buildings.

Only portraits of the reigning king should be displayed, he said in a message in French posted on his website dated Wednesday.

"This would totally conform with rules and protocol and the unchangeable traditions of the royalty and that of other royalties around the world," he said.

"The only figure in a portrait should be the actual king, not ... their predecessor."

Sihanouk also said that when the government distributes social and humanitarian aid, it should stop giving out portraits of himself and his wife.

Cambodians revere 82-year-old Sihanouk, whom they affectionately call the "king father", and grouped portraits of Sihanouk, former queen Monineath, and King Sihamoni are common across the capital.

When Sihamoni makes public appearances and greets his people, crowds wave both his portrait and Sihanouk's.

In a separate message, Sihanouk said he had quit as president of the National Supreme Council of Borders, a body set up to defend the territorial integrity of Cambodia.

He accepted the border council position in April, but complained on the day of its first meeting in Beijing in May that it was effectively powerless and could only advise the Cambodian government.

Sihanouk, who has vowed to live in quiet retirement after his surprise abdication, gave no reason for resigning.

Settling Cambodia's border disputes is a matter close to the heart of the former king, who has been at the fore of Cambodia's political life for decades.

The ex-monarch accuses Vietnam of encroaching on Cambodian soil, and alleges unjust treaties were signed in the 1980s which gave land to its neighbor during the occupation by its forces, which ousted the brutal Khmer Rouge regime.

Sihanouk is in Beijing undergoing chemotherapy to treat a reappearance of stomach cancer which was first diagnosed in 1993. He frequently communicates through his website, whether at home or abroad.