Lao, Thai, and Their Next of Kin: The Peninsular Branch of Southwestern Tai

This article reevaluates the subgrouping of Southwestern Tai languages using early phonological innovations reflected in Old Thai and Old Lao inscriptions. By analyzing four shared consonantal changes, simplification of *kʰr-, coalescence of *ɓl-, aspiration of *ʰr- and occlusivization of *x-, the research results propose a “Peninsular Southwestern Tai” subgroup encompassing Thai, Lao, Southern Thai, and most of the so-called “PH” varieties. This proposal offers a more empirical analysis of the genealogical relationships among these languages and suggests a southward spread of Peninsular Southwestern Tai from northern Laos to southern Thailand.