Pierra Vejjabul was the first female physician of Thailand who used to take a position in the Thai Ministry of Public Health's Department of Venereal Diseases. She was well known for her mother-and-child welfare establishment and her receipt of Khrueang Ratcha Itsariyaphon An Pen Thi Choet Chu Ying Chang Phueak prize.
Pierra was born to Trongkij Hoontrakul, a well-to-do merchant, and Phant Hoontrakul, who was his third wife. She used to take up a teaching position at Assumption Convent and Saint Joseph Convent Schools. Pierra obtained a medical education at the University of Paris, graduating in 1936 and then returning to practise in Thailand.
Pierra spent her whole life for medical career and her personal life was not public.