This article provides a comprehensive analysis of the little-known “bare classifier phrase” construction in Modern Standard Thai. It describes the syntax, semantics and discourse functions of Thai bare classifier phrases, and further proposes a diachronic account of their origin in reduction of post-posed numeral ‘one’. Following this synchronic and diachronic description, this article attempts to locate Thai within a working typology of bare classifier constructions in mainland Asian languages, and further argues for the importance of bare classifier constructions to the theory of classifiers more generally. Following Bisang (1999) and others, it argues that bare classifier constructions reveal the core function of classifiers in Asian languages to be individuation – a referential function. It therefore cautions against some recent proposals to merge classifiers and gender markers within a single categorical space defined on the semantic basis of nominal classification, and in favour of continuing to treat classifiers as a discrete linguistic category – in mainland Asian languages, at least.