This study aims to improve the Conformity of Production (CoP) testing process in a motorcycle manufacturing plant in Thailand to enhance operational efficiency, reduce lead time, and lower costs associated with test scraps. Value Stream Mapping (VSM) was utilized to analyze the current process and identify waste, and a Fishbone Diagram was used to analyze the root causes of problems. The process was then improved by applying the ECRS principles (Eliminate, Combine, Rearrange, Simplify) to eliminate unnecessary steps, reduce redundancies, and optimize resource management. The results showed that the number of process steps was reduced from 15 steps to 11 steps, and the total lead time decreased from 8.2 days to 5 days. These improvements enabled the timely return of motorcycles to the warehouse and reduced test scrap costs by 320,760.54 THB per year. Furthermore, the improvements maintained product quality standards in compliance with legal regulations and market requirements. This study highlights the significance of applying Lean Manufacturing principles to minimize waste and improve efficiency in the manufacturing industry.