Following the idea advanced and developed by a growing number of researchers in which a sentence may involve two tiers of meaning (e.g., Karttunen 1973, Karttunen and Peters 1979, Potts 2005, Roberts et al. 2009, Bosse et al. 2012, Bruening and Tran Ms., Kim, to appear), this paper suggests that (i) in Thai thuuk and doon are syntactic heads which are associated with two dimensions of meaning in multidimensional semantics, an at-issue meaning (i.e., the main assertion of a sentence) and a not-at-issue meaning, and that (ii) the adversative meaning that is implicated in thuuk and doon constructions is projected as a not-at-issue meaning, similar to the case in the Vietnamese bị constructions (Bruening and Tran, Ms.). Further, I shall show that only the short form is a passive construction and the long form is not (Bhatt and Pancheva 2006, Bruening and Tran, Ms.). Despite this distinction, I will show that the two forms involve a null operator A’-movement. Therefore, the long form and the short form receive the same semantic analysis; thuuk and doon contribute the adversative meaning, yet, they can be distinguished by the complement that thuuk and doon select.