Nor Aeni Indah Kurniasari Pengarang Niken Kencono Ungu, M.Pd Dosen Pembimbing 2 Buntara Adi Purwanto, S.S., M.Pd. Dosen Pembimbing 1 Niken Kencono Ungu, M.Pd Penguji 2 Rochyani Lestiyanawati.,M.Pd Ketua Penguji Buntara Adi Purwanto, S.S., M.Pd. Penguji 1

This study investigates the impact of Thai students' firstlanguage (L1) on their English pronunciation within the context ofEnglish as a Foreign Language (EFL) at Bakong Pitthaya Schoolin Thailand. The researcher used a descriptive qualitative methoddesign on a case study with Contrastive Analysis Theory onEnglish pronunciation. Recorded interviews and pronunciationtesting were the main techniques of data collection instruments. The subjects of this research were secondary grade students ofBakong Pitthaya School Pattani, Thailand. The results of this studyaimed to provide actionable recommendations for the teachers toenhance pronunciation instruction and improve studentpronunciation skill. This research contributes to the understandingof L1 influence on L2 pronunciation, offering insights that caninform teaching practices in similar EFL contexts. Keywords: L1, Pronunciation, EFL, Phonology, Pattani Malay, Contrastive Analysis