Teo joined the
Security and Intelligence Division (SID) in 1970, before becoming Director in 1979, a post he served until 1994. From 1982 to 1986, he held the position of
Director of the Internal Security Department concurrently. He was Permanent Secretary for Defence from 1994 to 2000 and Permanent Secretary in the Prime Minister's Office from 1998 to 2005. He was Singapore's High Commissioner to Australia from 2006 to 2008. He served as Chairman of the Public Service Commission from 2008 to 2018, Chairman of the Presidential Council for Religious Harmony from 2017 to 2019 and Senior Advisor of Temasek International Advisors Pte Ltd from 2019 to 2020. Teo was appointed as Chairman of the Council of Presidential Advisors on 2 January 2019. ==Awards==