In order to teach explicit speech acts appropriately according to the context of specific conversational situations, a study on linguistic and sociocultural differences between the learner’s native language and Korean must precede. Therefore, the object of this study is to diagnose the various aspects of refusal speech acts conducted by Thai Korean Learners (TKL) including strategy, linguistic expression, and contents of utterance, and to sample the items that are prone to pragmatic failure. The study first required twenty Korean Native Speakers (KNS) to evaluate the relevance of TKL’s utterances and confirmed that pragmatic failures are more likely to happen in contexts where the listener is at a higher social position. Then the study conducted a DCT to collect data on forty-two TKL, and analyzed the patterns in realization of refusal speech acts in comparison to their native language Thai. The results showed that TKL may use the same refusal strategy as KNS but their linguistic expression or the contents of refusal may be inappropriate due to the impact of their native language. The value of this research lies in analyzing the Korean learner’s problematic utterances pointed out by KNS from various aspects including strategy, linguistic expression, and contents of utterance in comparison to the learner’s native language. Such diagnosis will help better understand where exactly the learners make pragmatic failures and improve the teaching methods of pragmatic teaching.
