This study aimed to provide a theoretical framework for the validation of KSL speaking assessment using the argument-based approach. As outline of the model for the validation process, the argument-based approach to validity as presented by Michael Kane was evaluated. The argument-based approach provides a framework for test score interpretation; its use is supported by appropriate and validated evidence. Based on Kane’s test validation approach, which constructed the claim and assumption of inferential processes, the argument-based approach described the assessment validation procedure into interpretive argument and validity argument. The validation of KSL speaking assessment using the argument-based approach was designed to support claims on the intended purposes of the assessment. This study presented each model of interpretive argument related to KSL speaking assessment for summative and high-stakes proficiency assessments.