[7][9] In 1982 Siddarthan, with the assistance of Eelam Revolutionary Organisation of Students, went to Syria to receive military training from Palestinian militant groups.

[14][15][16] He contested the 2001 parliamentary election as one of the DPLF's candidates in Vanni District and was re-elected to Parliament.

[24][25] After the election he was appointed to assist the Chief Minister on vocational training, entrepreneurial development, small and medium enterprises.

[26] He took his oath as provincial councillor in front of PLOTE Secretary and All Island Justice Peace Subramanian Sathananthan at Chunnakam on 14 October 2013.

[27][28][29] Siddarthan contested the 2015 parliamentary election as one of the TNA's candidates in Jaffna District and was re-elected to Parliament.