Sangaree became interested in politics at an early age and in 1955 joined the Lanka Sama Samaja Party, the leading leftist party in Ceylon at that time. He was the LSSP's candidate for Kotahena South Ward at the 1959 Colombo Municipal Council election against the incumbent mayor V. A. Sugathadasa but failed to get elected. He was persuaded to stand as the LSSP candidate in Kilinochchi at the March 1960 parliamentary election even though he had no connection to the area. He lost. He stood again at the July 1960 and 1965 parliamentary elections but was again defeated on each occasion.