Abstract:
This thesis aims to (1) analyze the graphemic system of Sukhothai inscriptions, (2) compare vowel length contrast represented by the graphemic system of Sukhothai inscriptions with that in Proto-Southwestern Tai and Angkorian Khmer, the most import donor language during the Sukhothai period, and (3) analyze vowel length contrast in the Thai language of Sukhothai period based on the Sukhothai graphemic system. The study reveals that Sukhothai vocalic grapheme could be divided into two groups. Those in the first group are ones with length contrast, including the graphemes representing (i), (ɯ), (u), (o), (ɔ) and (a). On the other hand, those in the second group do not show length contrast, including the graphemes representing (e), (ɛ), (ɤ) and diphthongs (iə), (ɯə) and (uə). In addition, comparing length distinction of Sukhothai graphemes with vowel phonemes in Proto-Southwestern Tai and Angkorian Khmer, most of the graphemes agree with the contrast in Proto-Southwestern Tai, although a few show length distinctions different from PSWT. The graphemes representing (o) and (ɔ) show length contrast, while phonemes *o and *ɔː in PSWT do not. The discrepancy is from the large number of Angkorian Khmer loanwords. The correspondence between the graphemes and proto-phonemes reveals that there are two sets of Sukhothai vowel phonemes. The phonemes with length contrast are monophthongs /i, iː/ /ɯ, ɯː/ /u, uː/ /e, eː/ /ɤ, ɤː/ /o, oː/ and /a, aː/. On the other hand, the phonemes without length contrast are monophthongs /ɛː/ and /ɔː/, and diphthongs /iə/, /ɯə/ and /uə/. In conclusion, the Thai language of the Sukhothai period contains vowel length distinction.