(1) Background: Thailand is a major migrant receiving country and pioneer of migrant health policy in the ASEAN region. However, on the ground, coverage of migrants is faced with multiple barriers. (2) Objectives: We aim to scope and analyse the types of available evidence on migrant health coverage in Thailand and identify knowledge gaps. Specifically, we characterise the literature along year of publication, migrant subpopulation, health domain, scope of coverage, methods, study design, objectives and results. (3) Methods: We searched PubMed, Web of Science, Google Scholar, Cochrane Database, Worldwide Science and the Asian Citation Index for peer-reviewed and grey literature in October 2021 for studies analysing original data on health coverage of migrants in Thailand. To conceptualise health coverage, we used the three dimensions availability, accessibility and acceptability. (4) Results: 101 articles were included in the final analysis. Sixty-three were published after 2016, 39 focused on migrant workers and 18 on migrants in general. Forty-two concentrated on health in broader terms, followed by reproductive and maternal health (n = 31). Thirty-eight assessed coverage of specific services and 36 health coverage in general. Migrants themselves and key informants were the main data sources in 80 and 43 of the articles, respectively. Forty publications were qualitative, while 38 applied quantitative methods (22% descriptive; 7% analytical). Among the health coverage components, 79 articles included aspects of accessibility, followed by acceptability (n = 59) and availability (n = 30). (5) Conclusions: While there is a high number and broad range of studies on migrant health coverage in Thailand, we found that research on migrant subgroups, such as victims of trafficking and migrant children, as well as on the health domains, non-communicable diseases and occupational and mental health is neglected.