The typicality effect delineates a graded membership structure during categorization, whereby a typical item is easier to be judged as a member of a category than is an atypical item. The current study brought experimental evidence of the typicality representation of advanced Thai learners of Chinese, in order to compare the organization of the mental lexicon in the learners’ second language and first language. Three types of instances (i.e., typical in both Chinese and Thai (C1), typical in Chinese but not in Thai (C2), and typical in Thai but not in Chinese (C3)) in five categories (i.e., BIRD, VEGETABLE, FRUIT, FURNITURE, APPLIANCE) were presented in instance-category order. The response time of typicality judgement showed a similarity between natives and L2 learners, but that the response time of second language learners to C1 was not significantly longer than that to C2. These results suggested that high proficiency could modify the construction of a qualitatively native-like typicality representation, and that language-specific typicality was still beyond conceptualization in second language.