Challenging behaviors are one of the basic problems that all pre- and in-service teachers have to be prepared to deal with in schools. In Thailand, it was found that challenging behaviors of students with disabilities had an effect on teachers' stress because many teachers perceived that they were lacking the knowledge and skills to deal with these problems. The primary purpose of this study was to evaluate the effectiveness of a modified version of a basic functional assessment (FBA) training package developed by Loman and Horner (2014) on increasing the knowledge and skills of Thai special education teachers with respect to the functional behavior assessment process. This process is a set of procedures developed in the United States for assisting practitioners in identifying appropriate function-based interventions in which the motivations of students are taking into account (Dunlap & Fox, 2011; Dunlap, Kern-Dunlap, Clarke, & Robbins, 1991; Foster-Johnson & Dunlap, 1993; Horner, 1994; Horner & Carr, 1997; Lane, Umbreit, & Beebe-Frankenberger, 1999). The original research questions from the Loman and Horner (2014) study were used. However, this study also examined whether a modified version of this training package would be effective within the cultural context of Thailand and whether it would be perceived as effective and acceptable by Thai special education teachers for implementation with Thai students in a Thai school. Twelve special education teachers who worked at a laboratory school in Thailand participated in this study. Nine of these special education teachers were randomly assigned to be in the intervention group, which received the training. The three remaining teachers were randomly assigned to the control group and did not receive the training. The results across a variety of measures indicated that all trained special education teachers increased their knowledge of the FBA process after receiving the training. Using a questionnaire that assessed the social validity of the training procedure, it was found that these teachers perceived the training as efficient, valuable, and acceptable for use by Thai teachers with Thai students in Thai schools. A number of recommendations are made based on this study with respect to how to improve the training process when used in Thailand or another country outside of the United States. Nevertheless, the most important finding of this study was that these procedures were effective in preparing these teachers to use the FBA process with their students. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]