After his return to Siam, the prince advised King Chulalongkorn on the creation of a permanent general staff for the Royal Siamese Army.
As a result, he was appointed its first Chief of Staff in 1898.
In the same year his father also made him a Privy Councillor.
In 1899 he was given the additional role of Secretary of the Army and Commander of the Regiment of the King's Own Bodyguard.

In 1901, at the age of 24 he was appointed Commander of the Department of Military Operation, equivalent to the Commander of the Army.
In 1903 the prince was instrumental in the effort to reform the army by creating a system of regional conscription and training.
In 1905 the prince introduced the western concepts of organising the army into regiments, divisions and army corps.
He began by creating ten infantry divisions and founding many new regiments.

After the death of his father in 1910, he was appointed by the new king, his younger brother, Vajiravudh as the Minister of Defence.
In 1911 he was promoted to the rank of Field marshal (the highest rank in the army), the second such appointment in Siam.
As minister, in 1912 the prince approved the sending of three trainee air pilots to train in France, presaging the foundation of the Royal Thai Air Force.
The prince suffered from many illnesses and spent much of the last year of his life recuperating in Europe.
The prince died in office on 4 February 1913, at the age of only 36.
After his return to Siam, the prince advised King Chulalongkorn on the creation of a permanent general staff for the Royal Siamese Army. As a result, he was appointed its first Chief of Staff in 1898. In the same year his father also made him a Privy Councillor. In 1899 he was given the additional role of Secretary of the Army and Commander of the Regiment of the King's Own Bodyguard.
In 1901, at the age of 24 he was appointed Commander of the Department of Military Operation, equivalent to the Commander of the Army. In 1903 the prince was instrumental in the effort to reform the army by creating a system of regional conscription and training. In 1905 the prince introduced the western concepts of organising the army into regiments, divisions and army corps. He began by creating ten infantry divisions and founding many new regiments.
After the death of his father in 1910, he was appointed by the new king, his younger brother, Vajiravudh as the Minister of Defence. In 1911 he was promoted to the rank of Field marshal (the highest rank in the army), the second such appointment in Siam. As minister, in 1912 the prince approved the sending of three trainee air pilots to train in France, presaging the foundation of the Royal Thai Air Force. The prince suffered from many illnesses and spent much of the last year of his life recuperating in Europe. The prince died in office on 4 February 1913, at the age of only 36.
Chirapravati Voradej