The thesis examines the preservation of audiovisual heritage in Mainland Southeast Asia, with a focus on the Thai Film Archive and the Vietnam Film Institute. It examines the interplay of environmental, technological, and socio-political factors that threaten the long-term survival of film collections and shape preservation strategies across the region. The research focuses on the transition from analog to digital technologies in archival practices, highlighting that archival efforts are deeply embedded in local cultural values and involve ongoing negotiations among regional and global stakeholders. While digitization improves accessibility, it also raises concerns about technological obsolescence, the lack of specialized expertise, and precarious digital carriers and infrastructures. To address these challenges, the thesis advocates for sustainable, context-specific approaches, including safeguarding analog film processing knowledge, regional cooperation, shared infrastructures, and community engagement, to secure the legacy of Southeast Asian film heritage.