In Malaysia, research on the essential vocabulary for academic comprehension among pre-university and university ESL students is rather limited. This study introduces the "Comprehension Corpus" to pinpoint critical words vital for reading understanding. This study aims to develop the Malaysian University English Test (MUET) Reading Corpus, in order to identify the vital vocabulary for text comprehension and the specific categories or word lists that improve reading based on their texts coverage in the text. In addition, the vocabulary size needed to comprehend the comprehension texts was identified. By analysing CEFR-aligned texts using tools like RANGE BNC-COCA and WordSmith, it was found that to comprehend 98% of the content, students needed familiarity with 8,000-word families. this extensive demand, a streamlined list of 100 words, grouped by frequent topics and enhanced with the New General Service List (NGSL) and New Academic Word List (NAWL), was developed. The research underscores the necessity for educators to adopt targeted vocabulary teaching methods, highlighting the interplay between vocabulary breadth and reading comprehension. This tailored approach aids teachers in addressing students' specific lexical needs, ensuring more effective academic reading outcomes.