This chapter presents an overview of the structure and characteristics of SME and entrepreneurship activity in Thailand, including data on numbers and sizes of SMEs and their contribution to total employment and GDP. The performance of the SME sector is examined in terms of job creation, productivity, enterprise dynamism, numbers of high-growth firms and the contribution to trade and investment. The numbers and characteristics of entrepreneurs are also examined as well as regional variations of SME activity across Thailand. The chapter concludes with an analysis of the fundamental structural and enterprise-level challenges faced by SMEs and entrepreneurs.