Marie Thomas completed her studies at STOVIA in 1922 and was acknowledged as the first female graduate of STOVIA.[11] She then started her medical practice at the main hospital in Batavia (now Jakarta) called Centrale Burgerlijke Ziekeninrichting (CBZ) (now Dr. Cipto Mangunkusumo Hospital).[12][13] She would subsequently work in Medan, Manado, and back to Batavia at Budi Kemuliaan Hospital, a hospital established by the SOVIA foundation.[14][15] Thomas at one point became an assistant to Nicolaas Boerma, a Dutch physician who specialized in obstetrics.[16][17] She was one of the first doctors to deal with birth control and intrauterine devices.[18]