Sivarajan is currently the Secretary General of PSM since 2015 and he is graduated from UKM in the field of Chemistry. Before taking on the current position, Sivarajan has served the Treasurer of the Party from 1998 till 2015. Among other things, Sivarajan has also served as the Secretary of Dr. Nasir Hashim when he was the ADUN Kota Damansara and served as councilor at MBSA from 2008 till 2013.
He is also one of the founding members of PSM in 1998; Community Development Centre (CDC), 1992: a grassroot group working with plantation workers , factory workers , urban pioneers and orang asli, was a Coordinator of Coalition of Urban Pioneers under Jaringan Rakyat Tertindas Malaysia (JERIT).
He is still the Coordinator of Coalition Against TPPA. Sivarajan has championed and led various issues including fuel hike, decent housing for estate workers and urban pioneers, minimum wage act, and retrenchment fund for workers, and many more.