He was the elected State Legislative Assemblyman for Bukit Nenas, Selangor from 1969 to 1974 and served as Member of Parliament for Kuala Lumpur Bandar/Bukit Bintang from 1974 to 1990, until he left the DAP party and retired from politics in 1990.
Since then he has been a social activist and continued to serve the country. He is Chairman of the National Institute of Occupational Safety & Health (NIOSH), the Chairman of the National Service Training Council, Vice-Chairman of the Malaysia Crime Prevention Foundation, and member of the KL City Hall Advisory Board. He has served as a member of the Special Royal Commission to enhance the operations and management of the Royal Malaysian Police.
Lee is active in the private sector, he serves as a non-executive director in Media Prima Berhad, MBM Resources Berhad, and AMDB Berhad. As an Independent Non-Executive Director of Media Prima Berhad, Lee is the Chairman of the Nomination Committee, a member of the Audit Committee and Remuneration Committee of Media Prima Berhad.
He has written a book, entitled, As I Was Saying: Viewpoints, Thoughts and Aspirations of Lee Lam Thye. He is a highly regarded social activist in this region.