Currently Sim is the Deputy Minister of Agriculture and Agro-based Industry since 2018.
Sim is also the current Member of Parliament for Bayan Baru, Penang.
He is the Strategy Director from People's Justice Party (PKR), a component of Pakatan Harapan (PH) government coalition.
He previously served as the Penang State Legislative Assemblyman for Pantai Jerejak from March 2008 to May 2013.
He is the former political secretary to former Deputy Prime Minister of Malaysia and President of PKR Anwar Ibrahim.