While in the United States, Sim founded the Malaysia Forum Organization in Stanford University, a group promoting civil society and discussion of Malaysian issues.
Working under Anwar, he played a significant role in the release of a video clip purporting to show the fixing of judicial appointments and court decisions.
[3] In the 2008 general election, Sim contested in the Penang state constituency of Pantai Jerejak under the PKR ticket.
[3] In the 2013 general election, Sim contested the parliamentary seat of Bayan Baru instead and won to be a Member of Parliament.
On March 14, 2010, he sent a total of 2,108 signatures collected within two days from voters around the Bayan Baru market and the Fairgrounds in Sungai Nibong, Penang to Bayan Baru's independent MP Datuk Zahrain Mohamed Hashim and urged him to vacate his seat before The House of Commons convened on 15 March 2010.