Over the last two decades, research on world cities and global cities has unsettled the nation-state as the default unit of analysis in many disciplines in Anglophone social science. Rather than seeing the world as comprised of a mosaic of national political and social units, alternative geographies of networks connecting cities and urban regions have risen to prominence. In this paper, I consider the implications of such alternative mappings for Southeast Asia, bringing urban studies and area studies into critical conversation with each other. Geographies of urban networks extending across national borders challenge the ingrained methodological nationalism of conventional area studies, not least in Southeast Asia. However, to what extent do framings of trans-national urban connections among Southeast Asian or Asian cities mean that methodological nationalism has simply been up-scaled to methodological regionalism? In the first of the two main sections of the paper, I look in detail at the network spatialities brought into view by global and world cities scholars and consider their implications for regional urban systems frameworks. Flows of people, money and ideas extending from cities in Southeast Asia to cities beyond that region, and even trans-continentally, arguably imply that areal framings melt into network geographies which are global in scope. In the second section of the paper, I consider three types of regional formations that have been identified in research on globalization: the global triad regions, region states, and inter-Asia flows of capital; models and people which I examine do not map onto conventional cartographies of Southeast Asia. Together, these two sections of the paper serve as a reminder that in future research regions need to be specified empirically rather than assumed to exist as a priori framings for research, and that the geographies of ‘actually existing’ regionalizing processes are often very different from area studies mappings of the world.