[citation needed] He hastily returned to Oudong, the royal capital of Cambodia, to prevent his half-brother, Prince Si Votha from seizing the throne.

However, Norodom never truly complied with the French, and signed a secret treaty with siam, still acknowledging their suzerainty over Cambodia, and allowed them to keep Battambang and siem reap, which the Thais conquered in 1795.

Moving the royal court to Phnom Penh, Sisowath gave his full support to the French colonial regime.

During his reign, Sisowath continued Norodom's role in government, where he was well rewarded by the French for his cooperation: they built him a new palace, gave him a steam-powered yacht, and supplied him with a complementary ration of 250 lbs of high-grade opium per year.

[citation needed] Sisowath also helped modernise Cambodia, cooperating with French officials to build railways from Phnom Penh to Battambang, overseeing the construction of a modern throne hall in the royal palace, replacing the previous wooden structures in 1919, as well as building schools such as Preah Sisowath highschool, many wats and pagodas, an advanced pali-sanskrit institution, and the creation of the National Museum of Cambodia to store and preserve priceless treasures from the Khmer's great Angkorian past.

[citation needed] He is regarded and revered as one of Cambodia's illustrious kings, able to maneuver through the current political climate, and not only restoring national territorial integrity, reclaiming the great temples of Angkor, from Siam but also modernising the once feudal Khmer kingdom.

[citation needed] On April 24, 1904, the day King Norodom died, the Royal Crown Council met, gathering senior ministers and personalities of the kingdom, in order to elect the new sovereign.