In a letter posted on his website received Friday and dated Thursday, the octogenarian former monarch outlined a conversation he said he had had with Sihamoni on the day of writing.
"My beloved son told me, 'Papa, please do not worry - your darling son could return to
"I will hire a small room and stay with my wife, have a simple bathroom and eat simple food I can buy from a simple shop," Sihanouk quoted his son as saying.
Sihamoni is currently a bachelor.
He also said Sihamoni would refuse contact with journalists.
In the letter, entitled 'The Real Story', Sihanouk warned of a possible upcoming upheaval in the monarchy.
Sihanouk shocked many when he abdicated in 2004, citing advancing age and ill-health, and Sihamoni, previously an ambassador to the United Nations Education Scentific and Cultural Organization and a classical dancer before his ascension to the throne, took the reigns.
Fluent in French and Czech, Sihamoni, 55, was initially little known to ordinary Cambodians due to his long overseas career but has earned adoration in a country which recognizes kings as demi-gods.
He has eschewed politics, unlike his mercurial father during certain periods of his reign, who strutted the world stage.
Sihamoni's half-brother and Sihanouk's son, Prince Norodom Ranariddh, is currently in exile after being convicted for breach of trust in absentia and sentenced to 18 months in jail for his role in selling the headquarters of his former political party, Funcinpec.