PromptPay is Thailand’s national digital payment system, which was launched in 2017. It has reshaped financial transactions and government services in promoting a cashless society. This system offers a fast, secure, and cost-efficient alternative to traditional payment methods. This paper explores the broader impact of PromptPay focusing on its ability to enhance government efficiency, reduce corruption, and create opportunities for financial inclusion. PromptPay has significantly cut costs by simplifying processes such as tax refunds, welfare payments, and charitable donations, and at the same time, increased transparency and accountability. At its core, PromptPay serves as a platform for knowledge sharing within public administration. It enables government agencies to make more informed decisions and improve service delivery. This study employs cost-benefit analysis to assess the economic and operational advantages of PromptPay. The study also points out how it has driven Thailand’s digital transformation and supported the country’s shift toward a knowledge-driven governance model. At the end, the study provides lessons for Thailand and other nations, which seek to implement digital payment systems to achieve more efficient and transparent public administration.