Mah joined Parti Gerakan Rakyat Malaysia in 1993. He was attracted by the party's struggle for a just, fair and egalitarian Malaysia. Mah steadily rose up the party ranks and held many positions at all the division, state and national levels. In 2003, Mah was elected as the National Youth Chairman of Gerakan and the Chairman of Teluk Intan Gerakan Division. He was also appointed by the then Party President, the late Tun Dr Lim Keng Yaik as a member of the Party's highest decision making body, the Central Working Committee. Mah also served as the Secretary of the Gerakan Perak State Liaison Committee from 2005 to 2008. In the 2008 Party election, Mah was elected as one of the party's three elected vice-presidents' with the highest votes. In the aftermath of the 2013 General Election, Mah was also appointed as the Secretary-General of Gerakan after the resignation of Teng Chang Yeow. In the 2013 Party Election, Mah was elected as the Party President of Gerakan by defeating Teng Chang Yeow, the Chairman of Gerakan Penang State Liaison Committee. Mah stepped down on 16 September 2018 and was succeeded by Dominic Lau Hoe Chai as Party President of Gerakan
Mah was elected as the state assemblyman of Pasir Bedamar in the Perak State Legislative Assembly in 1995. Pasir Bedamar is one of the two state seats that form the Teluk Intan Parliamentary Constituency, the other being Changkat Jong. In 1999, Mah contested Teluk Intan Parliamentary Constituency and defeated Raj Nallaiya of the Democratic Action Party. In 2004, Mah was reelected as the Member of Parliament of Teluk Intan by defeating Wu Him Ven of the DAP and N. Gobalakrishnan of the People's Justice Party. In the 2008 General Election, Mah was defeated by M. Manogaran of the DAP and it was Mah's first electoral loss since his debut in 1995. The loss corresponded with BN's loss of its customary two-thirds majority in parliament. However, Mah continued to operate a service centre and assisted the voters of his hometown to the best of his ability. In the 2013 General Election, Mah was once again defeated; by Seah Leong Peng of the DAP with 7,313 votes majority. However, in early 2014 Seah died of cancer, necessitating the 2014 Teluk Intan by-election. Mah accepted the nomination of the party and BN to contest as its candidate for the by-election while DAP nominated Dyana Sofya Mohd Daud as its candidate. After an intense 14 day campaign, Mah prevailed narrowly by 238 votes majority. Mah was dubbed the comeback kid of BN. Mah lost and failed to retained his seat in the 2018 General Election.
