Achieving universal health coverage (UHC) is a priority of most low- and middle-income countries, reflecting governments' commitments to improved population health. However, high levels of informal employment in many countries create challenges to progress toward UHC, with governments struggling to extend access and financial protection to informal workers. One region characterized by a high prevalence of informal employment is Southeast Asia. Focusing on this region, we systematically reviewed and synthesized published evidence of health financing schemes implemented to extend UHC to informal workers. Following PRISMA guidelines, we systematically searched for both peer-reviewed articles and reports in the grey literature. We appraised study quality using the Joanna Briggs Institute checklists for systematic reviews. We synthesized extracted data using thematic analysis based on a common conceptual framework for analyzing health financing schemes, and we categorized the effect of these schemes on progress towards UHC along the dimensions of financial protection, population coverage, and service access. Findings suggest that countries have taken a variety of approaches to extend UHC to informal workers and implemented schemes with different revenue raising, pooling, and purchasing provisions. Population coverage rates differed across health financing schemes; those with explicit political commitments toward UHC that adopted universalist approaches reached the highest coverage of informal workers. Results for financial protection indicators were mixed, though indicated overall downward trends in out-of-pocket expenditures, catastrophic health expenditure, and impoverishment. Publications generally reported increased utilization rates through the introduced health financing schemes. Overall, this review supports the existing evidence base that predominant reliance on general revenues with full subsidies for and mandatory coverage of informal workers are promising directions for reform. Importantly, the paper extends existing research by offering countries committed to progressively realizing UHC around the world a relevant updated resource, mapping evidence-informed approaches toward accelerated progress on the UHC goals.