The term optimal currency area refers to an area that, as a single geographical domain, forms a single currency or multiple currencies whose exchange rates are irrevocably fixed. In this area, currencies fluctuate only toward the rest of the world. An optimal currency area is described as an area in which the excess of benefits over costs are realized. The aim of this paper is to understand the importance of forming an optimal currency area and to consider the possibility of forming an optimal currency area in the Southeast Asia region, based on understanding of different models of optimal currency areas and the contributions of many authors. The optimality of the currency area is defined by the criteria set by the theory of the optimal currency area, which primarily include economic openness, labour mobility and other factors of production, flexibility of prices and wages, diversification of production, similarity of inflation rates, and fiscal and political integration, and more. The development of the currency area optimality criteria provides the basis for examining the possibility of forming an optimal currency area in the Southeast Asian countries. This paper seeks to theoretically reinforce the possibility of forming an optimal currency area in the case of Southeast Asia. When considering the possibility of forming an optimal currency area, the reasons for the formation of a currency area in the Southeast Asia region are primarily stated, after which the fulfilment of the criteria of the optimal currency area in the Southeast Asia region is analysed. At the very end of this paper, conclusion is based on the analysis of the characteristics of the economy of Southeast Asian countries, the reasons for the formation of the specified currency area, the mentioned criteria that the currency area must meet in order to achieve optimality, and the cost-benefit analysis that would result from the formation of the currency area in the Southeast Asia.