Scientific publications are no longer practised by only a few established countries. The scholarly literature increasingly acknowledges that global science is pluralising. However, the existing literature mostly focuses on the national and global scales of science and overlooks the regional scale, especially regions in the Global South. This paper investigates the regionalisation of science of the Association of South-East Asian Nations (ASEAN), a ten-nation entity. It envisions science space to be multi-scalar, consisting of individual, institutional, local, national, regional and global scales. Specifically, it develops an agential approach to analyse patterns of intra-ASEAN scientific collaborations and funding in a multi-scalar science space, with a particular focus on the actors in this space and the structure in which these actors are embedded. The analyses of the bibliometric data of ASEAN countries in the last twenty years indicate an increasingly integrated regional science space in ASEAN. The intra-region collaborative publications grew faster than the total publications. The countries have increasingly funded their own and each other's research. Malaysia emerges as a central actor in the regional scientific connectivity, despite Singapore having the most scientific publications to date.