University Admission Tests in Thailand are important documents which reflect Thailand's education system. To study at a higher education level, all students generally need to take the University Admission Tests designed by the National Institute of Educational Testing Service (NIETS). For the English test, vocabulary and reading comprehension is one of the key elements. In order to prepare for and pass the test, students should learn and accumulate an adequate amount of vocabulary. The purpose of this research is to conduct a documentary study on the scattering and lexical profiles of Thailand University Admission Tests. Fifteen papers covering 55,161 running words were analyzed in a framework of two word lists: General Service List (GSL) and Academic Word List (AWL). The results showed that the coverage of GSL and AWL are 85.05% and 4.58%, respectively. A combination of the GSL and the AWL covers 89.63% of the texts. For the coverage and reading comprehension, a 4,000-word level for reasonable comprehension covers 94.82% of the texts. It is suggested that both the GSL and the AWL could be good sources for students to learn so as to prepare for the test and to study at an advanced level in university.