In this article, algorithm for transforming sign language into Thai alphabets is presented to fill the gap in communication between the hearing impairment and normal people. Leap Motion Controller was applied to detect 5-fingertip position and palm center in the form of X and Y axis. Then, decision tree was created by using the Quadtree technique and the research result on transforming Thai sign language into finite automata was applied to improve algorithm in creating finite automata of Thai alphabet sign language to increase efficiency and speed in processing sign language. The test result shows that it can discriminate 44-Thai alphabet sign language at 72.83% accuracy.