The researchers have asserted thesis writing's important role and demanding nature for EFL postgraduate students. However, the experience of writing an EFL postgraduate thesis in non-native English-speaking contexts has been relatively neglected. Besides, most of the previous studies have been confined to genre analysis or text-based interpretation. The available literature indicates a need to explore the process of writing a thesis from the writers' perspective. The current research aims to explore what EFL postgraduate students experience when writing a thesis at a university in northeastern Thailand. Fifteen EFL graduate students from eight disciplines participated in the study. First-hand accounts were collected through written narratives and semi-structured in-depth interviews. The thematic analysis finds that the practice of thesis writing, challenges & strategies, and emotions contributed to the students' perceptions of the experience. EFL postgraduate thesis writing is more than writing itself. It is also a site for the students to develop scholarly identity and exercise agency. The students encountered linguistic, personal, and social challenges. Despite the challenges and emotional ups and downs along the journey, the students learn to handle the writing practice and strive toward the desired acceptance as newly emergent members in academia.