This study has its objectives: 1) to compare students' English reading competency before and after learning through the collocational instruction (CI) for improving undergraduate student skills in English reading and writing: 2) to investigate students' English writing competency after learning through CI. The target group was 20 undergraduates, selected by Purposive Sampling, at Mahachulalongkornrajavidyalaya University, Khon Kaen Campus, majoring in Buddhist Studies, Philosophy, Teaching Thai Language, Political Science and Social Studies. The research tools included: 1) the CI lesson plans; 2) a reading test; and 3) a writing evaluation form. The statistics used in the data analysis were: Mean, Percentage and S.D. The results were as follows. 1) the reading competency of the samples is higher after learning by CI and that writing is also higher than the set criteria.