Prior to entering politics, Koh was a colorectal surgeon and medical researcher. He made his political debut in the 2013 by-elections as a PAP candidate contesting in Punggol East SMC against candidates from three other opposition parties, garnering 43.37% of the vote and losing to the Workers' Party's Lee Li Lian, who won 54.5% of the vote.
In the 2015 general election, Koh contested in Ang Mo Kio GRC as part of a six-member PAP team and won with 78.64% of the vote. Koh was elected as the Member of Parliament representing the Yio Chu Kang ward of Ang Mo Kio GRC. In the 2020 general election, he joined the PAP team contesting in Tampines GRC and won with 66.41% of the vote.
During the campaigning, Koh had called himself "kaki lang" ("one of us" in Teochew) and "son of Punggol". When reporters asked him about his family's ownership of two cars, he had said, "everybody has a car, we have two... We are professionals, we need to travel." His words were perceived as a blunder and reeking of elitism. After losing the election, he admitted that he had misspoken, saying, "It's not logical, even an idiot wouldn't say that. So it was partly my fault."[9]
In the 2015 general election, Koh joined the six-member PAP team contesting in Ang Mo Kio GRC[10] Following the results of the election, Koh was elected into Parliament when the six-member PAP team won and clinched 78.64% or 135,115 of the electorate's valid votes in the constituency.[11] and they won with 78.64% of the vote against the Reform Party. Koh thus became a Member of Parliament representing the Yio Chu Kang ward of Ang Mo Kio GRC.
On 1 January 2016, Koh was appointed Minister of State at the Ministries of National Development and Trade and Industry. On 1 May 2017, he was promoted to Senior Minister of State and continued serving in the two Ministries; he relinquished his position in the Ministry of National Development on 30 April 2018. On 23 April 2018, Koh was appointed Deputy Secretary-General of the National Trades Union Congress[12] and he held this position until 15 May 2021.[13]
A Chinese Singaporean of Teochew descent, Koh grew up in a farmhouse at Lorong Cheng Lim in Punggol before he and his family moved to a four-room HDB flat in Toa Payoh. His father was a bus driver who drove the public bus service 82.[17] Koh was the oldest child in his family and often worked part-time jobs when he was young to support his family.[17]
Koh is married to a doctor, with whom he has two daughters.[7]
^ abKoh, Mui Theng; Tan, Judith (13 January 2013). "Meet the 'son of Punggol'". The New Paper. Singapore Press Holdings. asiaone. Archived from the original on February 17, 2016. Retrieved 9 January 2016.
The party affiliation of each member is indicated right after the constituency/seat he or she represents. PAP: People's Action Party; WP: The Workers' Party; PSP: Progress Singapore Party All of the leaders of the respective GRCs are in underline. MP(s) who is go on a leave of absence is in italic. NMPs do not belong to any party.
The party affiliation of each member is indicated right after the constituency he or she represents. PAP: People's Action Party; WP: The Workers' Party NMPs do not belong to any party. There were two terms of NMPs in this parliament, with nine NMPs in each term.
