This study is aimed at comparing and contrasting topic shift devices in two types of Thai conversations: television programme interviews and casual conversations. It is found that topic shifts in Thai can be classified into three categories according to turn taking, namely old turn topic shift, new turn topic shift, and overlap topic shift. In addition, they can be categorized into three types based on coherence or topic maintenance, namely coherent shift, renewal shift, and noncoherent shift. Five other types of topic shifts based on meaning of new topics include self-oriented topic shift, other-oriented topic shift, self/other-oriented topic shift, environmental topic shift, and general knowledge topic shift. The result of frequency analysis shows that new turn topic shifts occur more frequently than other types of turn topic shifts and occur both in interviews and casual conversations. Overlap topic shifts, on the other hand, occur only inthe latter type of conversation. Coherent shifts are found to characterize interviews, whereas noncoherent shifts occur most in casual conversations. Other-oriented topic shifts are found to appear most in interviews and environmental topic shifts in casual conversations. Three topic shift devices are found to characterize Thai conversation: word/phrase devices, sentence/utterance devices and implicit devices. The result of frequency analysis matches the hypothesis of the study in that sentences devices occur in interviews more than in casual conversations, whereas the other two types of devices occur more in casual conversations. The result of the study concerning the relationship between topic shift types and topic shift devices contrast to the hypothesis. Topic shift devices do not correlate with topic shift types but correlate with types of conversation. The majority of topic shifts in interviews use word devices and sentence devices respectively, whereas the majority of topic shifts in casual conversations employ word devices and implicit devices respectively.
