Professor Toemsakdi started his academic career in 1956 as an associate member of the Institute of Chartered Accountants in England and Wales at the Faculty of Commerce and Accountancy, Chulalongkorn University, where he taught intermediate accounting, advanced accounting & auditing, and finance. He was appointed head of accounting and finance, and then Dean in 1971. From 1975-1977, he served as President of Chulalongkorn University. He then retired from full time service at Chulalongkorn University. He was managing partner of Deloitte (Thailand) until 2005. Concurrently, he was the founder and Director of Chulalongkorn Language Institute from 1978-1982. He then founded Sasin in 1982 and served as Director until 2014.