In the context of EFL learning, speaking is considered one of the important language skills to learn. Thai students have been learning English from primary school to university level, however they still do not speak in it fluently as expected. One of the factors which hinder them from being able to speak fluently is anxiety. Hence, this study was carried out to identify the levels of speaking anxiety in the EFL classroom in one of Southern Thai districts as well as the causes of it. This study utilized qualitative research design. The data were obtained through Foreign Language Classroom Anxiety Scale (FLCAS) questionnaire and an in depth interview. The subjects involved were eleventh graders of a private high school in Southern Thailand. The data were then analyzed applying qualitative data analysis. The study findings showed that among the subjects, it was found out that most of them were in in medium and high level of anxiety. Meanwhile shyness or unconfident, afraid of making mistakes, grammar concern, lack of vocabulary, and being laughed at by others were the five major causes that contribute to the students’ anxiety in learning English.