The authors are developing a talking robot based on the physical model of human vocal organs in order to reproduce human speech mechanically. Humans use speech in daily communication, and each different country has a different language. The complex movements of vocal organs generate different vocal sounds. This study focuses on the performance of the talking robot to reproduce Vietnamese language, which is a tonal language and contains many unvoiced sounds and fricative sounds. The mechanical system of the talking robot is modified by adding an unvoiced sound source for fricative sound generation and a new flexible vocal cords. The control of the artificial vocal cords is adjusted to give the tonal effect. The robot is programmed to speak several Vietnamese phrases, and the output speech is evaluated by questionars.