In many developing societies, education systems have not traditionally emphasized the development of leadership capacities among school principals. This is the case in Thailand, where principals have been criticized both for corruption and for being a 'weak link' in education reform. This study examined "authentic leadership" practices of school principals in Thailand and sought to link these with teachers' academic optimism and work engagement. Using qualitative data drawn from a larger mixed methods study, this report presents a case study which describes the authentic leadership practices of one principal in the Thai context. Qualitative data were collected from semi-structured interviews with the principal and teachers as well as from information contained in school web sites and reports. The findings show how a principal who models behaviors associated with the dimensions of authentic leadership can shape the attitudes of teachers and create a climate that is conducive to change. The study highlights the importance of values as a critical basis for developing leadership capacities for change. The findings from this contextualized description of authentic school leadership in Thailand contribute to a growing of studies designed to build a more diverse knowledge base in educational leadership.