The objectives of this study are to: 1) investigate and demonstrate the model of transformational leadership, and to demonstrate the mediating effects of organizational culture and high performance work systems on SME performance in Thailand; and 2) develop a causal model linking transformational leadership, organizational culture, high performance work systems, and SME performance in Thailand. The Office of Small and Medium Firms Promotion's database has 545 small and medium-sized enterprises that are divided into 110 retail and wholesale companies, 204 service companies, and 231 manufacturing companies.