This essay delves into the complex interplay of social determinants of health in the context of HIV/AIDS, specifically comparing the situations in Australia and Thailand. The essay focuses on sex workers as a vulnerable group and examines the impact of two key social determinants: economic conditions and gender. It explores how these factors influence HIV transmission, prevention, and treatment access within the chosen countries. The essay highlights the differing patterns of HIV prevalence and transmission, and analyzes the social, economic, and cultural factors that contribute to vulnerability. It also discusses the role of healthcare systems, government policies, and societal attitudes in shaping the HIV/AIDS epidemic among sex workers in both countries. The analysis includes a discussion of the impact of social stigma, legal frameworks, and access to resources on the health outcomes of the vulnerable population. The essay concludes by emphasizing the importance of addressing social determinants to effectively combat the HIV/AIDS epidemic and promote health equity.