Regulatory impact assessment (RIA) is a pivotal tool for shaping and enhancing the quality and effectiveness of laws (Davidson et al., 2021). This research focuses on comparing RIA mechanisms in the Organisation for Economic Co-operation and Development (OECD) member countries and Thailand. It involves analyzing RIA criteria, methodologies, impact assessment report preparation, and quality assurance for legislation. Employing qualitative research methods, the study employs document analysis, in-depth interviews with key informants from legislative, administrative, and legal sectors, individuals impacted by laws, and experts in various fields. Content analysis was employed. The study emphasizes the crucial roles of the government and Parliament in RIA development. Delegating RIA responsibilities to independent organizations aims to reduce legislation volume and improve its quality, contributing to a “good parliament” and an “effective government” following democratic principles and the Thai Constitution of 2017. The research underscores Parliament’s crucial role in standardizing law impact assessment. This promises better legislation quality, transparency, and accountability, aligning with global standards and encouraging public participation for improved governance and societal well-being.