Quantitative and qualitative restrictions on the distribution of lexical tones in Thai

In present-day Thai, contour tones show a more restricted distribution in comparison with level tones that cannot be explained by syllable structure alone. This diachronic study argues that both quantitative and qualitative restrictions are responsible for the puzzling gaps and accounts for them by positing Optimality-Theoretic constraints. In addition, it analyzes the tonal distribution in the early 19th and 20th centuries based on data from published materials. Furthermore, it discusses sound changes and lexical changes that gave rise to the tonal distribution.