[4][5][6] At the time of his birth and that of his younger brother, his mother Princess Monique who is of Khmer, French and Corsican descent, had been one of King Norodom Sihanouk's consorts after being a constant companion since the day they met in 1951 when she won first prize in a national beauty contest.

When he was in his preadolescence years, he starred in a production of Pyotr Tchaikovsky's The Nutcracker at the prestigious Prague National Theatre, where he pursued private ballet and piano classes and was once even selected for a television rendition of Brundibár, a well-known children's opera.

[15] Between 1971 and 1975, Sihamoni completed his higher education in classical dance and music at the Academy of Performing Arts in Prague, culminating with the attainment of a Master's degree for which he wrote a thesis titled The Conception and Administration of Artistic Schools in Cambodia.

He lived in France for nearly 20 years and continued his pursuit in the arts, establishing 'Ballet Deva', an original dance troupe, in which he served as its General Manager and Artistic Director, alongside heading the Royal Khmer Cinematic Corporation.

[39][40] Then-Prince Sihamoni's accession to the throne was reflected upon by journalist Michael Sheridan of The Sunday Times whom on 17 October 2004 remarked: The extraordinary story of the aesthete who flies home this week to become king of Cambodia — and of the men who nearly had him killed — can be summed up for most people in the capital, Phnom Penh by the tale of two buildings on the banks of the Mekong River.

Two momentous dramas in Cambodia's modern history – the chequered rule of King Sihanouk and the [Khmer Rouge's] blood-drenched attempt to create a Marxist utopia – are therefore drawing to a close at the same time.

[50][51] On 12 December 2008, it was reported that Sihamoni had selected twenty-six members of the Cambodian royal family to his advisory court, among them his half-brother and former Prime Minister Prince Norodom Ranariddh as chief advisor and president of the council.

[67][68][69] Some Cambodian opposition figures, however, have called for him to be more vocal and directly involved in the political issues of the country, like his predecessor, King-father Norodom Sihanouk was, contending that the King has the constitutional prerogative to do so, in terms of powers accorded to him.

[76] This is reinforced by analysis from observers that Sihamoni "has represented both continuity and change — withdrawing royalty from active politics, but advancing it as a symbol of national reconciliation", thereby restoring the "monarchy's traditional role as an 'umbrella' under which Cambodians could unite.

In 2005, in the first major political challenge of his reign, it was reported that he was hesitant to authorize the royal assent for the government's plans to give effect to a controversial border treaty with neighbouring Vietnam, which was compounded by his predecessor, King-father Sihanouk's objection.

[84][85] In 2006, at the government's petition, he granted a pardon to leading opposition politicians, namely Sam Rainsy and Cheam Channy, who originally had their parliamentary immunity annulled and were facing charges viewed as politically motivated.

[93][94][95] In 2009, Sihamoni, upon considering the appeals made to him for the review of the conviction verdict against opposition-affiliated journalist and editor Hang Chakra, who was jailed on charges of "criminal disinformation", sought the government's support for a prospective royal pardon.

[107][108][109][110] Consequently, in what is regarded as the first time he had intervened directly to try to resolve a political dispute, the King attempted to play a mediating role and urged for national reconciliation, by exercising his moral authority to facilitate talks between the two party leaders, Rainsy and Prime Minister Hun Sen.

[116][117] After this, in August 2014, Sihamoni would formally swear-in Rainsy and the CNRP members of parliaments who had up until then, refused to assume their seats in the National Assembly because of the dispute, though he had earlier officiated Prime Minister Sen's and CPP lawmakers' swearing-in ceremony in September of the previous year due to a constitutional necessity.

[131][132] Regardless, commentators noted that it added to a perception that Sihamoni tends to be overseas to avoid having to give his signature to highly contentious legislations and that such trips are supposedly timed, which then trigger a delegation of responsibility to the next constitutional office holder.

[161] At the ASEAN summit in November 2022, Sihamoni hosted regional leaders at the royal palace where he reinforced Cambodia's commitment to the bloc of nations and emphasized the continued importance of inter-state collaboration in addressing contemporary issues.

This included the centrality of peace in relation to socio-economic development, healthcare and educational investment, concern regarding the Myanmar conflict, the impact of increasing tensions between global powers, the threat of nuclear weapons, climate change, and the lingering effects of the COVID-19 pandemic.

[182][183][68][184] This can be soon through various examples such as in 2006, where when the relocation of one of the campuses of the Royal University of Fine Arts caused an inconvenience to students and teachers, including posing safety concerns, he arranged for the donation of three minibuses to assist with transportation.

[192] At times, he has even assisted his fellow citizens first-hand during adverse events, such as venturing out into flooded areas and handing out goods to victims directly[193] and was once reported to have requested for his official state car to stop so he can give a blanket to an elderly Cambodian who he saw on the roadside.

[191] Additionally, Sihamoni is said to donate to the Cambodian Red Cross on a regular basis[194] and has authorized royal grants for infrastructure,[195] schools,[196] orphanages,[197] struggling communities,[198] religious institutions,[199] people affected by a disability,[200] rehabilitation centres,[201] mental health organizations,[202] victims of violence,[203] and sponsoring student's trips[204] among others.

[218][219] In September 2012, he presided over the opening of L'ombrello di Beatocello, a documentary film by Georges Gachot showcasing the life's work of famed Swiss pediatrician Beat Richner and his contribution to Khmer society.

[220][221] Likewise, in February 2017, he did the same at the global premiere of acclaimed Cambodian-based film First They Killed My Father, documenting the experiences of Loung Ung, a survivor of the Khmer Rouge and directed by Oscar-winning actress Angelina Jolie, whom he had earlier hosted, along with her family, at The Royal Residence in Siem Reap prior to the occasion.

[247][248] In November 2023, the King inaugurated the formal ceremonies to commemorate the completion of restorative works for the western causeway into Angkor Wat and its reopening, which was closed for several years due to its deteriorating condition.

[77][78][79][134] Scholar Milton Osborne, regarded as amongst the world's most distinguished authors specializing in Southeast Asia,[286][287] commends him as a "dedicated servant of his people" that is "cultured and disciplined",[26] but he questions the monarchical institution's long-term survivability.

[294][295][296] Prominent Cambodian history professor Sambo Manara credits Sihamoni as a "morale model" for all Khmer people whom exudes a calm and kind demeanor, underscored by a sincere warmth towards his subjects, notwithstanding some misconceived notions about the King's role from within some sectors of the population, in particular, the youth demographic.

[230][297][298] Reflecting after a royal audience with the King in 2013, then International Monetary Fund Managing Director Christine Lagarde expressed how she was profoundly touched by his "thoughtfulness and compassion" and how he "not only cares deeply about the welfare of his people, but is clearly passionately devoted to promoting the cultural and artistic heritage of his country.

"[299] On the occasion of his 68th birthday, ASEAN described King Sihamoni as a monarch who is "cherished and well-respected by the people of Cambodia" and as someone who exemplifies "dignified and humbled leadership", characterized by his frequent engagements with the populace through local visitations.

[306][307] In February 2018, the penal code was formally revised to incorporate lèse-majesté legislation, which makes it an offence to insult the king, pursuant to its promulgation by Cambodia's National Assembly and Senate, and the law came into effect the following month.

[323] In some respects, Sihamoni is regarded somewhat as an enigmatic figure, with the available literature pointing to a "reflective, deliberate and cultured man" who apparently had reservations in becoming king, yet in spite of this, humbly assumed the solemn responsibility of his position, whilst holding "his cards close to his chest.

[343][344] In June 2015, he was bestowed the honorary religious title Preah SriLoka Dhammika Raja (Khmer: ព្រះស្រីលោកធម្មិករាជ), or "Virtuous King for the Propagation of Buddhism in the World", which was recommended for him at the Sixth Buddhist Summit in the year prior in December 2014.