This research aims to study the relationship between corporate governance assessment and performance: A case study of listed companies in the Stock Exchange of Thailand. The data was collected from the Corporate Governance Report of Thai Listed Companies and the Thai Institute of Directors with excellent very good and good CG scores for five consecutive years. The data obtained was based on financial statements annual reports and annual registration statements (Form 56-1) from 2015 to 2019 for 214 companies in total. Descriptive and inferential statistics were used for data analysis i.e. Pearson’s correlation coefficient and multiple regression. The findings revealed that corporate governance i.e. the proportion of independent directors the proportion of managerial ownership CEO authority merging and the proportion of meeting attendance of the board had a positive relationship with the performance of listed companies with significance levels of 0.01 and 0.05. The measurement was based on gross profit margin (GPM) return on assets of shareholders return on sales (ROS) and earnings per share (EPS).