The purpose of this study was to establish the factor structure and dimensionality of the Metacognitive Orientation Learning Environment Scale -- Science (MOLES-S) in the Thai context. The metacognitive orientation of a science classroom learning environment is defined as the extent to which psychosocial conditions that are known to enhance students' metacognition are evident in a specific science classroom. This study builds on earlier work in the research areas of science education, metacognition, and learning environments. A sample of 5418 Thai science students in grades 10 to 12, from 40 schools across Thailand, completed the MOLES-S that had been translated into Thai. Exploratory factor analysis was undertaken and Rasch analysis was used to calibrate the scale and explore its dimensionality. The results suggest that the MOLES-S(T), where (T) represents Thailand, has the same factor structure as the original MOLES-S, is reliable, and can be used with confidence in research into metacognition in Thai high school science classrooms.