Assistive technology has a significant impact on helping students with communication disorders achieve their academic goals. Selecting an appropriate assistive technology for a student requires parents, educators, and other professionals take a comprehensive view, carefully analyzing the interaction between the student, the technology, the tasks to be performed, and the settings where it will be used. It is important for the researchers to have better understanding of this disability issues and develop their own tool. Foreign assistive technologies are expensive and not readily available for the student with communication disorders in Thailand. It is therefore desirable to design and develop such tools for the student in Thailand and determine its effectiveness on performance of the student. Consequently, this paper obviously is considered on a study to integrate usability testing into the design and development of two assistive technology tools called Thai Word Search program and Thai word prediction program. Thai Word Search program assists student with communication disorders to write any vocabulary that he/she cannot spell it correctly. However, Thai word prediction has its advantages for students with communication disorders as the function of word completion and word prediction. Finally, the study indicated that student with communication disorders in this study increase his ability in writing when using assistive technology more than without using assistive technology. The result for the first tool shows the value of p is 0.00001. Additionally, result for the second tool shows the value of p is 0.00027. Therefore both results are significant at p ≤ 0.05.