In August 1992, after stepping down as Chief of Air Force, Teo began studying at Tufts University, and graduated with a Master of Arts in international relations in 1993.

[6][7] During his career in the military, Teo has also held the appointments of squadron commander and Head, Air Operations Department.

[7][8] Teo was appointed as the first Commander of RSAF from 1 November 1985 to 31 April 1990, and later as the first Chief of Air Force on 1 May 1990.

[1][2] Under his leadership, the RSAF acquired eight new General Dynamics F-16 Fighting Falcon, operationalised the 145 Squadron with 20 ST Aerospace A-4SU Super Skyhawk, and equipped the island with air defence systems.

[5][12][13] On 21 January 2002, Teo was appointed as high commissioner to the United Kingdom, while concurrently serving as the ambassador to Ireland, before stepping down in July 2011.