Aye Ko joined Myanmar Armed Forces on 20 April 1952 as second lieutenant for 2nd Company in No. 15 Infantry Battalion. He was promoted to the rank of lieutenant on 30 April 1953. He was transferred to No. 30 Infantry Battalion and promoted to the rank of captain on 8 July 1955. On 27 July 1956 Aye Ko was transferred to No. 2 Military Intelligence Company attached to 8th Infantry Brigade. He became General staff officer at the headquarters of 8th Infantry Brigade on 30 October 1956. He was then transferred to No. 30 Infantry Battalion on 25 May 1960 as temporary deputy battalion commander. He was promoted to the rank of major on 3 June 1961 and became deputy battalion commander for No. 30 Infantry Battalion. He was transferred to No. 1 Shan Rifle Battalion on 17 June 1963. He was promoted to the rank of lieutenant colonel and became commanding officer of No. 1 Shan Rifle Battalion on 20 January 1964. Aye Ko was posted to South Western Regional Military Command as colonelgeneral staff officer on 9 September 1964,. On 2 June 1966, Aye Ko was transferred to Military Operations Department at the Ministry of Defence as colonel general staff officer. He took over the role of director of the Directorate of Artillery and Armour Corps within the Ministry of Defence on 30 July 1966. Aye Ko was posted to 88th Light Infantry Division on 24 April 1967. He was promoted to the rank of full colonel on 17 August 1968 and became deputy division commander for 88th. On 3 July 1969 Aye Ko became division commander of the 88th. He subsequently rose through the command positions as commander of Strategic Operation Command on 24 January 1972, commander of North Eastern Regional Military Command on 11 July 1972, commander of North Western Regional Military Command on 8 March 1974, commander of Yangon Regional Military Command on 18 March 1975. He was promoted to the rank of brigadier general on 2 April 1976 and became Vice Chief of Staff. He was promoted to major general on 1 January 1979 and to lieutenant general on 13 March 1981 and became Chief of Staff. Aye Ko resigned honorably from Myanmar armed forces on 19 September 1981.
