In this study, productions of 10 Thai words with an five tones, namely high, mid, low, falling and rising were elicited from 3 native Thai speakers and 6 native English speakers, who had learned Thai in adulthood. A variety of acoustic measurements including voice onset time of the initial consonant, vowel length. the first and second vowel formants (Fl, F2) , peak, valley and range of the fundamental frequency (FO) of all the five tones, were taken on both native and non-native productions. The two groups were found to differ in almost an acoustic parameters measured, but significantly in the Fl, F2 and FO valley values. Two native and all 6 non-native productions were rated for accentedness by three native listeners. The rating data suggested that the nonnative production can be readily distinguished from the native production. Only some non-native production of some of the target words were considered to be native-like. More importantly, amount of the experience with Thai did not seem to affect the rating data. When the acoustic data were regressed on the means ratings, it was found that significant predictors varied from word to word (or from to tone).

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