This paper focuses on the implementation of Indonesia's free and active foreign policy in Southeast Asia, during the presidency of Suharto. It looks at a wide range of study cases from 1967-1998 that reflect how Indonesia’ free and active policy has shaped most of its interaction in the Southeast Asian region during the Cold War. The research adopts analytical-descriptive research methodology in interpreting Suharto’s policies in responding to the Southeast Asian political landscape. The paper concludes that the success of Indonesia’s free and active foreign policy in Southeast Asia during Suharto’s rule is based on (1) historical aspects of Indonesian kingdom dominance in Southeast Asia, (2) the political culture of Javanese ethnicity, (3) increasing military support that strengthened the regime’s power, and (4) aligned policies with dominant domestic institutions in Indonesia.