The dispute between Thailand and Cambodia was first occured since the seizure of territory along both country in ASEAN region. The adjacency between both countries do not reduces the possibility of conflict between them. With a certain norms which apply in a country, the unavoidable conflicts can be subjected. Thus, many norms which apply in those country will be reducing the conflicts and will be resolved with diplomacy between the states.ASEAN is a regional organization which conducts all the activities and the importance of the south east asian nations. ASEAN ables to overcome conflicts within their member states, such as the conflict between Thailand and Cambodia. As an organization, asean must be able to find a way to make peace among the nations. ASEAN roles as an active mediator in this conflict and must not be only in one side between those country, and ASEN has rules and norms which have to be maintained and followed by all of their member states. In this cases, ASEAN use negotiation method and diplomacy way to overcome the conflict in a reasonable and peaceful way.There are four influential factors in ASEAN norms: multilateralism practical, non intervention, asean way, and regional autonomy principle. There is also an alternative concept which has to be operate in ASEAN Way: Constructive Intervention Concept and Flexible Engangement Concept. ASEAN also offer a solution to reach a consensus in order that the conflict can be resolved. This research will analyze how asean roles in that conflict and how asean overcome the the conflict between its member states in a peaceful way.