By 2030, more than two-thirds of the global population will live in an urban environment, and an additional 70 M or more are projected to live in ASEAN cities. Sustainable urbanization will thus play an important role in the green economic growth of the ASEAN region, including Phnom Penh City, i.e., one of Southeast Asia's newest commercial hubs. However, rapid urbanization poses many prominent challenges such as waste management, energy management, and other environmental stresses that may lead to unsustainability. With the emergence of the fourth industrial revolution, building smart cities is an opportunity to embed and leverage technologies such as blockchain to promote sustainability, innovation, and inclusivity. Hence, this study focuses on understanding the problematique of blockchain adoption in the waste management sector through a systematic problem analysis using a novel T-Spherical Neutrosophic Fuzzy DEMATEL method. Potential barriers are identified through literature review and expert opinion. Linguistic assessments from the group of experts are aggregated to elucidate the causal map of the problematique. These present findings underscore the need for policy intervention to attract the initial capital investment for the physical blockchain infrastructure and strengthen the implementation of the legal framework of data privacy. Public awareness to increase the market acceptance of blockchain technology and the development of trustful cybersecurity systems are of great necessity. Further investigation should be done to understand how to attract the initial capital investment in high-tech industries by systematically analyzing the interaction among barriers in Cambodia's new context of science, technology, and innovation development.