Coursebooks as one of the major issues of language teaching/learning instruction can relieve the overburden as well as under-prepared teacher of a great deal of stress, time and additional work. Currently, both commercial and teacher-made English language teaching (ELT) coursebooks are available for use and seem flexible at hands. In any respect, however, usefulness of the coursebooks needs to be evaluated as claimed. To this end, the study, proposed as a new approach to lexical evaluation, examines the words occurring in three teacher-made ELT coursebooks used for compulsory foundation English courses in a Thai university as lexical syllabi are required to prepare university students for academic study at tertiary level. The RANGE program was employed to analyze the wordlists of the three teacher-made ELT coursebooks and it was found that those ELT coursebooks provided insufficient vocabulary size of general service words and academic words which were crucial to academic study regardless of syntactic structures. In addition, the three ELT coursebooks were frustrated for learners to survive unassisted reading in and outside the class. Application and suggestions are given for concerns and pedagogical practices.