The Asian EFL Journal January 2021, Volume. 25 Issue 1 48 What Makes More and Less Proficient EFL Learners? Learner’s Beliefs, Learning Strategies and Autonomy Phitsinee Koad Walailak University, Thailand Budi Waluyo Walailak University, Thailand Bioprofile Phitsinee Koad is an English lecturer at School of Languages and General Education at Walailak University, Thailand. She graduated with a Master’s Degree in Teaching English as a Foreign Language from Walailak University. Her research interests include varieties of English, learner autonomy, and CIPP model. Email: honey.koad@gmail.com Budi Waluyo is a full-time English lecturer at School of Languages and General Education, Walailak University Thailand. He finished his M.A. at the University of Manchester, U.K. and Ph.D. at Lehigh University, U.S.A. He received International Fellowships Program from Ford Foundation, USA, and Fulbright Presidential Scholarship from the U.S. government. His research interests involve education policy, educational technology, ELT, and international education. Email: budi.business.waluyo@gmail.com Abstract Undeniably, Individual Differences (IDs) between more and less proficient EFL learners are noticeable, yet there is still little known about factors underlying individual differences that make learners become more and less proficient as a result of their English language learning. This study, hence, explores three factors, involving beliefs, learning strategies, and autonomy that are presumed to be the causes of IDs among Thai EFL learners. Using BALLI, SILL and Learner Autonomy surveys, this study collected information from 722 (72.15% female, 26.73% male, 1.11% unidentified) university students studying General English (GE) courses in the Academic Year of 2019/20 at Walailak University, Thailand. The data were examined by using Exploratory Factor Analysis (EFA), Independent t-test, and Multiple-linear School of Languages and General Education, Walailak University, Academic Building 5, 222 Thai-Buri sub-district, Thasala District, Nakhon Si Thammarat 80160, Thailand