Based on the generalization and classification of passives in the world?s languages put forward by Givόn (1979), Siewierska (1984), and Keenan (1990) this study recapitulates the universal types of passive. Twenty types of passive are proposed. They are grouped into ten pairs of contrastive types; namely, passive vs. ergative, true passive vs. pseudo-passive, direct vs. indirect passive, sentential vs. lexical passive, personal vs. impersonal passive, plain vs. reflexive passive, neutral vs. adversative or favorable passive, basic vs. non-basic passive, synthetic vs. periphrastic passive, passive with patient subject vs. passive with non-patient subject. It is found that five of these pairs are applicable to the analysis of passive types in Thai. A typological system of passives in Thai is proposed. It comprises eight actual types of passive, which are distinguished from one another by these features: [true], [neutral], [direct], [basic], and [synthetic].