Prateep was born in the Klong Toey Slum in Bangkok. Prateep Ungsongtham spent four years at primary school and then started working. As a 12-year-old worker she began to save from meagre wages to pay for secondary education at night school.
Because most slum children could not go to a regular school, Prateep opened her own Baht a Day School at her home. She spent much time helping children and their families to cope with the conditions of slum life.
When the slum dwellers were threatened with eviction by the Port Authority of Thailand (PAT) Prateep pushed for a compromise solution, and the PAT made a new site available 1 km away. In 1976 Prateep completed her education with a Diploma of Education from Suan Dusit Teachers College.
In 1992 she became a committee member of the Confederation for Democracy and one of the leaders of the opposition to the military dictatorship of the time.
In Thailand's first free election in the year 2000 she won a seat in the Senate. Now she is caring for the rights of the poor and discriminated people on political level.
In 2004 she received the The World's Children's Prize for the Rights of the Child from Queen Silvia of Sweden.