The design of wind turbines has been continually evolving to enhance aerodynamic efficiency, which is crucial for improving energy conversion and reducing operational costs. One promising technique is the application of the Co-Flow Jet (CFJ) method, which utilizes simultaneous blowing and suction to augment aerofoil performance. Despite its potential benefits, the relationship between aerofoil thickness and the resulting improvements in lift and drag coefficients has not been thoroughly explored, especially for the NREL aerofoils commonly used in wind turbine applications. This study utilizes Computational Fluid Dynamics (CFD) simulations in order to investigate the aerodynamic efficiency improvements of the NREL S826, NREL S825, and NREL S818 aerofoils through the application of the CFJ technique. Various configurations with different blowing (B) and suction (S) configurations were tested, including 0.08B-0.7S, 0.08B-0.8S, 0.1B-0.7S, and 0.2B-0.7S configurations. The results demonstrate that the S826-0.2B-0.7S, S825-0.2B-0.7S, and S818-0.08B-0.7S configurations yield the most significant enhancements at a common momentum coefficient (Cm) of 0.08. Specifically, there were increases in lift coefficients by about 51.1%, 66.38%, and 109%, and improvements in lift-to-drag ratios by about 11.5%, 14.38%, and 146.18% for the S826-0.2B-0.7S, S825-0.2B-0.7S and S818-0.08B-0.7S configurations, respectively.