In this paper a detailed acoustic investigation of the difference between clear and breathy phonation types in the Chanthaburi dialect of Khmer is presented. The study of this dialect is of paramount importance since it may prove the only way to quantitatively evaluate the historical claim that Khmer once had contrasting phonation types. Data were collected from five speakers. The phonation types of the vowels were then investigated by means of a variety of algorithms that have been proposed in the phonetic literature, including harmonic-to-noise ratio [HNR; e.g., Wayland et al. (1995)]; H1--H2, where H1 and H2 refer to the amplitude of the first and second harmonic, respectively [e.g., Klatt and Klatt (1990)]; H1-A1, and H1-A3, where A1 and A3 refer to the amplitude of the most prominent harmonic in the region of the first and third formant, respectively [e.g., Stevens and Hanson (1994)]. A comparison of the different metrics will be presented. The results from some analysis methods show that the Chanthanuri dialect distinguishes clear and breathy vowels. The finding that there still is a dialect of Khmer with a phonation-type contrast provides crucial evidence for the historical reconstruction of Khmer phonology.