The purposes of this research were to study Buddhist concepts and personality traits for employee engagement, to develop a framework of sustainable employee engagement with Buddhist psychological traits, and, to validate a causal model for sustainable employee engagement with Buddhist psychological traits. Mixed methods research using the quantitative research to extend the qualitative research results was used for the research design. The key informants were 15 employees’ best practices using purposive sampling for qualitative research, and two-stage random sampling to obtain 540 employees for quantitative research. In-depth interview schedule and questionnaires were used for research instruments. Qualitative data were analyzed by using content analysis and analytic induction, and quantitative data were analyzed descriptive statistics using SPSS, and validation analysis of the causal model using LISREL. Research showed that there were 4 aspects of Buddhist concepts for employee engagement consisted of good heart, good speech, good sociable and good consistency behavior, and 4 aspects of personality traits for employee engagement consisted of conscientiousness, optimistic, adaptability and friendliness. These aspects were developed and divided into two variables called bases of sympathy and, personality traits. Moreover, sustainable employee engagement were contained in 4 aspects consisted of self-passion, self-dedication, self-evaluation and self-development. A developed model fit with empirical data. Result of model analysis showed that chi-square = 79.06; df = 63; p = 0.833; GFI = 0.98; AGFI = 0.96. Therefore, Buddhist psychological traits can use for the reinforcement of sustainable employee engagement for Thai people.