Purpose: In the context of Thailand's progress towards education reform, scholars have identified a lack of effective school-level leadership as an impeding factor. The purpose of this paper is to develop and validate a theoretical model of authentic leadership effects on teacher academic optimism and work engagement. Authentic leadership was considered a suitable model of school leadership in light of Thailand's explicit recognition of the importance of developing the moral capacity of students and emphasis on ethical leadership. Design/methodology/approach: The study employed a quantitative cross-sectional survey design. Survey data were obtained from 605 teachers in a nationally representative sample of 182 primary schools. The data were analyzed using confirmatory factor analysis and structural equation modeling. Findings: The results indicated that the model of authentic leadership effects on teachers' academic optimism and work engagement was validated. A moderate relationship was observed between authentic leadership and the dependent measures of teacher attitudes. Practical implications: The study identified a potentially important lack of alignment between the espoused values and actions/decisions of school principals in Thailand. When combined with prior research conducted on leadership for educational reform in Thailand, our findings highlight the systemic nature of the problem faced in changing traditional patterns of behavior in Thai schools. More specifically, despite change in the nation's educational goals, human resource management of the nation's school leaders continues to produce administrators and managers rather than leaders, either instructional or moral. Originality/value: The study extends prior studies of school leadership in the context of Thailand's education reform that focused more specifically on principal instructional leadership in Thailand. In addition, this study of authentic school leadership is one of only a few conducted outside of Western societies.