This study is about Thai English (ThaiE), a variety of World Englishes that is presently spoken in Thailand, as the result of the spread of English and the recent Thai government policies towards English communication in Thailand. In the study, I examined the linguistic data of spoken ThaiE, collected from multiple sources both in the U.S.A. and Thailand. The study made use of a qualitative approach in examining the data, which were from (i) English interviews and questionnaires with 12 highly educated Thai speakers of English during my fieldwork in the Southwestern U.S.A., Central Thailand, and Northeastern Thailand, (ii) English speech samples from the media in Thailand, i.e. television programs, a news report, and a talk radio program, and (iii) the research articles on English used by Thai speakers of English. This study describes the typology of ThaiE in terms of its morpho-syntax, phonology, and sociolinguistics, with the main focus being placed on the structural characteristics of ThaiE. Based on the data, the results show that some of the ThaiE features are similar to the World Englishes features, but some are unique to ThaiE. Therefore, I argue that ThaiE is structurally considered a new variety of World Englishes at the present time. The findings also showed an interesting result, regarding the notion of ThaiE by the fieldwork interview participants. The majority of these participants (n=6) denied the existence of ThaiE, while the minority of the participants (n=5) believed ThaiE existed, and one participant was reluctant to give the answer. The study suggested that the participants' academic backgrounds, the unfamiliar notion of ThaiE, and the level of the participants' social interaction with everyday persons may have influenced their answers to the main research question.

The historical study of sentence adverbs has, before now, been based mostly on models that emphasize the pragmatic and discourse-based motivations of processes of grammaticalization. This dissertation breaks from such tradition by exploring diachronic adverb development through syntactic and morphological lenses. A generative, feature-based approach is used that incorporates the cartographic architecture developed by Cinque and combines it with a more phenomenological approach to both grammaticalization and lexicalization. Cinque's hierarchy of speech-act, evaluative, evidential, and epistemic adverbs is analyzed. It is determined (through corpus data) that these subcategories have grown in use primarily during the Modern English era, and particularly during the nineteenth and twentieth centuries. These four subcategories can be divided into two groups that are more general: speech-act adverbs, which arise from a (conditional) speech-act clause that undergoes ellipsis, and the other three types, which all arise from copula clauses. Each of these two groups is considered, and different methods of reanalysis by speakers are proposed for each. In addition, a revised model for categorizing adverbs is proposed. This model is based on morphological lexicalization (or univerbation) processes, thus accounting for the wide variety of adverbial source materials. Such lexicalization offers a pattern for sentence adverbial formation. Finally, Standard Chinese adverbials are briefly examined, with results indicating that they show very similar signs of lexicalization (within the limits of the writing system).