He is a member, the State Deputy Chairman and the Division Chief of Hang Tuah Jaya of the Malaysian Chinese Association (MCA), a component party of the BN coalition.

[8] He was elected to the Malacca State Legislative Assembly as Kesidang MLA for the first term after defeating Lim Jak Wong of the Democratic Action Party (DAP) by a majority of 1,701 votes.

In 2007, Koh was appointed as Member of the Malacca State EXCO in charge of Housing, Local Government, Environment and Transportation by Chief Minister Mohd Ali.

He lost the seat and was not reelected as the Kesidang MLA for the second term after losing to Goh Leong San of the Pakatan Rakyat (PR) by a minority of 1,399 votes.

He won the seat and was elected to the Parliament as the Alor Gajah MP after defeating Damian Yeo Shen Li of the PR by the majority of 11,597 votes.