This paper presents Thai tone recognition. Fundamental frequency feature (F0) or differential F0 (ΔF0) is appended with Mel-Frequecy Cepstral Coefficient by employed Hidden Markov Model (HMM). The system used RSF/DRA (Running Spectrum Filtering/Dynamic Range Adjustment) [4] to eliminate noise andnormalize dynamic range speech feature. Average Magnitude Different Function (AMDF) is applied to extract maximum amplitude then F0 is calculated andadjusted by seam 3E method. The Thai tone recognition system is evaluated atoffice environment speech, white noise 10 dB SNR and 20 dB SNR. The experiments are conducted by means of isolated words: /pa:/ and /pu:/, which have 5 tones, mid/M/, low/L/, fall/F/, high/H/, and rise/R/. They arespoken by 12 speakers: 6 males and 6 females. The Thai tone recognition accuracy rates of F0 tone feature are 80%, 75% and 65% for office environmentspeech, 20 dB SNR and 10 dB SNR respectively, meanwhile F0 tone feature are 85%, 75% and 65% respectively.