BACKGROUND: Southeast Asian countries host signficant numbers of forcibly displaced people. This study was conducted to examine how health systems in Southeast Asia have responded to the health system challenges of forced migration and refugee-related health including the health needs of populations affected by forced displacement; the health systems-level barriers and facilitators in addressing these needs; and the implications of existing health policies relating to forcibly displaced and refugee populations. This study aims to fill in the gap in knowledge by analysing how health systems are organised in Southeast Asia to address the health needs of forcibly displaced people. METHODS AND FINDINGS: We conducted 30 semistructured interviews with health policy-makers, health service providers, and other experts working in the United Nations (n = 6), ministries and public health (n = 5), international (n = 9) and national civil society (n = 7), and academia (n = 3) based in Indonesia (n = 6), Malaysia (n = 10), Myanmar (n = 6), and Thailand (n = 8). Data were analysed thematically using deductive and inductive coding. Interviewees described the cumulative nature of health risks at each migratory phase. Perceived barriers to addressing migrants' cumulative health needs were primarily financial, juridico-political, and sociocultural, whereas key facilitators were many health workers' humanitarian stance and positive national commitment to pursuing universal health coverage (UHC). Across all countries, financial constraints were identified as the main challenges in addressing the comprehensive health needs of refugees and asylum seekers. Participants recommended regional and multisectoral approaches led by national governments, recognising refugee and asylum-seeker contributions, and promoting inclusion and livelihoods. Main study limitations included that we were not able to include migrant voices or those professionals not already interested in migrants. CONCLUSIONS: To our knowledge, this is one of the first qualitative studies to investigate the health concerns and barriers to access among migrants experiencing forced displacement, particularly refugees and asylum seekers, in Southeast Asia. Findings provide practical new insights with implications for informing policy and practice. Overall, sociopolitical inclusion of forcibly displaced populations remains difficult in these four countries despite their significant contributions to host-country economies.