Thai is often identified as a language that violates condition C of the binding theory, a grammatical constraint that has been claimed to be innate (Crain 1991). We present the first-ever experimental investigation of condition C in adult and child Thai. We show that (as per previous claims) Thai adults ‘violate’ condition C when the bound nominal is bare. When modified by a classifier, however, Thai referential expressions must obey condition C, thus showing that Thai does indeed adhere to condition C. We then show that Thai children (aged four to six years) apply condition C to all nominals, irrespective of whether they include classifiers. This ubiquitous adherence to condition C suggests that Thai children initially assume that condition C applies to all referential expressions. The implications for the universality and innateness of condition C are discussed.