Formants frequency adaptation is a procedure to adapt the formants frequency by parameter.This parameter is personality,tonal accent, pitch level and syllable duration.Personality is a parameter in sub procedure, which to adapt formants frequencies in a form of each personality such as man, woman or child. Everyone has a pitch range to which he or she is constrained by simple physics of his or her larynx. For men,the possible pitch range is usually found somewhere between the two bounds 50-250 Hz, while for women,the range usually falls somewhere in the interval 120-500 Hz. Tonal accent is a parameter in sub procedure,which adapts formants frequency in a form of thai tonal access by using Thai-Tonal-Accent Rules. This sub procedure is associated with the pitch contour over time and performs function in Thai language.Pitch level is a parameter in sub procedure to control frequency of speech. Syllable duration is a parameter in sub procedure to control speed of speech