In 1963 he graduated from the RTA Command and General Staff College, and one year later from the United States Army Command and General Staff College at Fort Leavenworth. During the 1960s and 1970s, Chavalit served in the communist insurgency suppression campaign in the jungles of Thailand, and prepared Thai soldiers for their operations in the Vietnam War. During the period after the October 1973 popular uprising, he was considered close to the "Thahan Prachathippatai" ("Democratic Soldiers") group, even though he did not openly identify as a member of the group.