From 1930 to 1934, he was provincial medical officer at Sakolnakorn where he developed in interest in providing comfort and easing the miseries of the mentally ill.
In 1935, he became assistant director of the mental hospital in Thonburi under Dr. Luang Vichien Patayakorn who sent the young man to study and observe medical practices in Japan, the Philippines, and Indonesia.
At that time, straitjackets were used to subdue mental patients but Phon and his colleagues pushed for reforms, banking instead on gentleness and love.
Upon his return he was assigned as chief of a division on welfare at the Ministry of Interior, establishing an orphanage school which promote mental hygiene.
[1] In 1942, he succeeded Dr. Luang to become the director of the Mental Hospital (Rong Phayaban Khon Sia Sati in Thai[2]) in Thonburi.