Prayoon's Thai father was Major Yam Pamornmontri, and his German mother, Annelie Pamornmontri (née Feuer), was a physician. His mother also taught
German to many Siamese cadets in the German Empire at the time, many of whom later became members of the
Khana Ratsadon. In Paris, Pridi and Prayoon often spent their free time meeting in
cafés or strolling the streets of Paris, talking about politics and the situation in Siam. This led to the creation of Khana Ratsadon, with Prayoon and Pridi as the first two members. The first official meeting of Khana Ratsadon was held at rental no.9,
Rue Du Sommerard on 5 February 1927, Prayoon's 30th birthday. His role in Khana Ratsadon was to contact and coordinate with other members. After absolute monarchy was overthrown in Siam, he was appointed
Minister of Education in the administration of Field Marshal
Plaek Phibunsongkhram, the
Prime Minister. After
World War II, he was appointed
Minister of Public Health (1954–1957). In the military, he founded the
Volunteer Defense Corps (VDC) and ascended to the rank of lieutenant general. He was elected as an
MP for Chiang Mai as a member of the Seri Manangkasila Party in the
February 1957 Thai general election. Prayoon's eldest daughter Yaowapa Pamornmontri married to Sombud Tuchinda with five children. His youngest son is actor, singer, and politician
Yuranunt "Sam" Pamornmontri. Prayoon Pamornmontri died on 12 August 1982, aged 85, in a crash on a Bangkok city bus at
Ratchaprasong Intersection. ==Honours and awards==