Overview
Senior Minister of Singapore is a position in the Cabinet of Singapore. Holders of this office have previously served as either the prime minister or the deputy prime minister. Among the executive branch officeholders in the order of precedence, the position ranks after the prime minister and the deputy prime minister. Senior Ministers also serve as part of the Prime Minister's Office (PMO) and work at The Istana.
Background
S. Rajaratnam, Singapore's first Minister for Foreign Affairs, took on the newly-created role of Senior Minister in 1985 before retiring in 1988. Prior to that, he served as Deputy Prime Minister between 1980 and 1985.
Lee Kuan Yew, Singapore's first Prime Minister, was appointed as Senior Minister in 1990, after being succeeded by Goh Chok Tong as prime minister. He was ranked second in the order of precedence, superseding the incumbent Deputy Prime Ministers Lee Hsien Loong and Ong Teng Cheong.
Goh Chok Tong was appointed Senior Minister in 2004 after handing over the office of Prime Minister to Lee Hsien Loong. As Senior Minister, he was ranked second in the order of precedence, while Lee Kuan Yew, who was appointed as Minister Mentor, ranked third in the order of precedence.
From Wikipedia (CC BY-SA 4.0).