, Chinese and Thai speakers. The relationship is inferred from their behavior concerning awareness and memory shown in the experiments. The hypothesis of this study is that speakers of English and Japanese, tense languages, are more awareness of and memorize... time better than speakers of Chinese and Thai, tenseless languages. The experiment of awareness is a picture – describing task. There were 109 participants (26 English; 30 Japanese; 22 Chinese; 31 Thai). The results show that English and Japanese

and expressive. The second part of this research concerns the use of na and si by native Thai speakers, Japanese learners of Thai, and English learners of Thai. The results show that in role play and pair discussion tasks, the overall uses of na and si...This dissertation aims to analyze communicative functions of the Thai final particles na and si and speech acts of utterances in which they occur, and to explore the use of na by Japanese learners of Thai and English learners of Thai, comparing