Benedict Anderson (1991) suggested ‘a Nation-state is an imagined political community. It is imagined as both inherently limited and sovereign’. Because of this imagination that a nation (-state) is ‘inherently exclusive’. Southeast Asian States seem to imagine their communities as exclusive, with certain categories of people being excluded, especially those who are considered different and those who cross (inter)national borders. This chapter intends to establish some frameworks for the book by unpacking the notion of borders, not only from territorial and geographical perspectives, but also the borders created within cultural, social and economic spheres. Through the concept of citizenship, the paper argues conceptually and empirically that borders created through ‘imagined community’ can easily discriminate against populations who are not considered as members of a political community or not ‘one of us’. Because of this concept, some are excluded from the benefits of membership, while migration has serious implications on citizenship policy, exclusion (from citizenship) exacerbates (forced) migration in the region.