Sâr spent three years in Paris. In summer 1950, he was one of 18 Cambodian students who joined French counterparts in traveling to Yugoslavia, a Marxist–Leninist state, to volunteer in a labour battalion building a motorway in Zagreb. He returned to Yugoslavia the following year for a camping holiday. Sâr made little or no attempt to assimilate into French culture and was never completely at ease in the French language. He nevertheless became familiar with French literature, one of his favorite authors being Jean-Jacques Rousseau. His most significant friendships in the country were with Ieng Sary, who had joined him there, Thiounn Mumm and Keng Vannsak. He was a member of Vannsak's discussion circle, whose ideologically diverse membership discussed ways to achieve Cambodian independence.