LP Thean has extensive legal and judicial experience. He was in legal practice in Kuala Lumpur from July 1958 to November 1964 and in Singapore from November 1964 to January 1984. He was appointed a Judge of the Supreme Court of Singapore in February 1984. He served as a Judge of the High Court from 1984 to 1993 and as a Judge of Appeal in the Court of Appeal from 1993 till his retirement in February 2002.

LP Thean is currently Chairman of the Competition Appeal Board, and Chairman of the Market Surveillance and Compliance Panel of National Electricity Market of Singapore.