The 1951 Convention relating to the Status of Refugees, together with its 1967 Protocol, is the foundation of the contemporary international refugee regime. Despite criticisms of Eurocentrism, the Refugee Convention continues to have a significant impact on regional conventions, national legislation, and evolving norms and standards. Within Southeast Asia, some scholars contend that the refusal of non-signatory States to accede to the Convention demonstrates their rejection of international refugee law. However, State practices suggest that even signatory States, despite their professed ‘acceptance’ of international refugee law, sometimes implement measures that contravene the Refugee Convention. In contrast, non-signatory States demonstrate varying degrees of contributions to the normative development of international refugee law. In the absence of treaty obligations, the Bangkok Principles on the Status and Treatment of Refugees serve as Southeast Asia’s primary non-binding normative framework for refugee protection. This article investigates recent developments in Thailand, a non-signatory State, specifically the establishment of the National Screening Mechanism (NSM). The article fills a significant gap in the growing body of research on the contributions of non-signatory States to the normative development and reinforcement of international refugee law by providing a detailed, country-specific analysis of Thailand’s recent legislation. Using the socialization theory of acculturation, this article contends that Thailand’s refusal to accede to the Refugee Convention does not constitute a rejection of international refugee law. Rather, it reflects Thailand’s commitment to align with international refugee law. However, a thorough analysis reveals that Thailand’s 2019 Regulation on the Screening of Aliens adopts a security-oriented framework by instituting national security exceptions at various stages of the NSM process, reflecting Thailand’s efforts to balance humanitarian concerns with national security priorities, with a discernible inclination towards the latter. The Regulation’s strong emphasis on national security suggests that Thailand’s acculturation to international refugee law is only partial. The research advocates for a rights-based approach to mitigate the negative consequences of the security-oriented framework, with the goal of improving refugee protection in Thailand.