Objective: The present study aimed to develop the Thai Psychological Capital Inventory as the standard assessment for Thai people by studying its validity and reliability.

Materials and Methods: The research process was conducted in 2 processes; (1) Document study: the process of gathering essential information to create the conceptual framework. The Thai Psychological Capital Inventory was developed in this process (2) Field study: the process of collecting data from the sample population: Thai people age between 12 to 87 years old. In this study, the data was collected from 2,855 with voluntarily acceptance of consent from.

Results: The results revealed that The Thai Psychological Capital Inventory consisted of 44 items for assessing 4 state-like components of Psychological Capital; hope, self-efficacy, resilience and optimism. The research instrument was validated by 5 experts: content validity and item objective congruence. The exploratory factor analysis fitted the pooled Thai Psychological Capital items by a principal component analysis, followed by a series of Varimax rotations and item analysis method that were performed. The reliability coefficient of total Thai-Psychological Capital Inventory was 0.98.

Conclusion: The research showed that The Thai-Psychological Capital Inventory was good psychometric properties and suitable for Thai people.

Keywords: Thai-Psychological Capital Inventory, Thai PsyCap