The aims of this research were 1) to investigate the Vocabulary Learning Strategies (VLS) of Thai students’ in learning English, 2) to find out the most dominant strategy used by Thai students and also 3) to find out the distribution level of Thai students related the most used strategy. The data were collected using Schmitt’s Vocabulary Learning Strategies Questionnaire (VLSQ). The questionnaire consisted of 31 statements administered to 4 Thai students in English Education Department of Universitas Muhammadiyah Purwokerto. Interviews were also conducted to obtain more information from the respondents. The results showed that Thai students used strategies namely looking up the word in English – Thai dictionary, checking if the word is also a Thai word, checking the word’s form; whether it belongs to verb, noun, adjective, looking up the word in English – English dictionary, asking classmates, pronouncing the word, taking notes, and using some English media. The most dominant strategy used by Thai students in learning vocabulary is determination strategy with the mean of 2.7 and the distribution level was categorized as high one, which means that most of Thai students always used the determination strategy to learn vocabulary.