Exploitative child labour is a serious issue in many countries across Asia (ILOIPEC 2013; Johnson 2011; IPEC 2009). Children working in commercial sexual exploitation (CSEC) are among the most vulnerable and marginalised groups in society and face grave risks to their safety, development and well-being. Despite these concerns there remains an absence of rigorous research to inform assessments of the prevalence of children engaged in CSEC. Basic data infrastructure is crucial to effective program planning and monitoring of outcomes.