Chulalongkorn died on 23 October 1910, and Vajiravudh succeeded his father as king of Siam.

On 28 November 1911 Vajiravudh's second and formal coronation was held with visiting royals from Europe and Japan as guests, a first for Siam, which festivities took 13 days. Later that year, the first airplane was flown in Siam.

Rama VI inherited his father's plan of building a modern nation although he was more skeptical of outside methods. Disagreements occurred incessantly with "old aristocrats", many of whom were his relatives such as the celebrated Prince Damrong, his uncle, who took charge of the Ministry of Interior. As more and more corruption in the newly created provinces was reported, Rama VI created a viceroy system. Viceroys, appointed directly by the king, were sent to supervise provincial governors and local officials.

During 1918-1919 the price of rice soared. The government faced public criticism due to its tepid response. The major cause of the problem was the hoarding of rice. Chinese millers and rice merchants bought huge amounts of rice from farmers for export to Singapore, the largest rice market in the region. Price speculation was rampant. The government imposed a ban on rice exports. At the same time, public servants asked for higher wages due to the rising cost of living. The public, mainly the urban "middle-class", and Chinese traders became more and more unhappy with the government.

In 1924, King Vajiravudh, accompanied by Suvadhana, visited the Federated Malay States. The reconciliation with European powers on unequal treaties progressed gradually, while the financial crisis was taking a great toll on Siam as another loan was taken from Britain and the firing of numerous government officials occurred. In 1925 Vajiravudh had to dissolve his Nakorn Sri Thammarat Regiment and merged provinces into larger units to lower maintenance costs.

On the night of 25 November, Princess Suvadhana gave birth to a princess only two hours before Vajiravudh's death. Vajiravudh glimpsed his sole daughter for the first and only time before his demise on the 26 November 1925. The throne passed to his brother, Prajadhipok, who named Vajiravudh's daughter as Princess Bejaratana.