The contemporary landscape of public administration in Thailand is undergoing a critical transition, characterized by the adoption of New Public Management (NPM) principles amidst a significant demographic shift in the workforce. This research investigates the factors influencing the management efficiency of government agencies within the Bangkok metropolitan area, a context currently challenged by a "brain drain" of the younger generation (Gen Z and Millennials) to the private sector. The study aims to empirically analyze the influence of four key independent variables: Perceived Organizational Support (POS), Organizational Transparency, Employee Engagement, and Knowledge Management (KM). Utilizing a quantitative research design, data were collected via a stratified random sampling method from 400 personnel working in various government agencies in Bangkok. The instrument employed was a 5-point Likert scale questionnaire, validated for Item-Objective Congruence (IOC) and reliability. Data analysis involved descriptive statistics and Multiple Linear Regression to test the hypothesized relationships. The expected findings suggest that while traditional stability remains a factor, modern drivers such as organizational support and knowledge management systems play a pivotal role in enhancing operational efficiency. This study provides crucial implications for policymakers and human resource directors in the Thai public sector, highlighting the need for transparent, supportive, and knowledge-centric environments to retain talent and maintain high performance in the post-COVID-19 era.