Lean Manufacturing has been widely adopted in various business and industries worldwide. To determine the current stage of Lean implementation in Thailand and the barrier Lean implementation, the qualitative research involving interview with 10 industrial companies practicing Lean manufacturing was conducted. The result from this study shows that most Lean practitioners understand the principal of Lean manufacturing. Different organization functions adopt different types of Lean tools and techniques as well as the performance measures depending on their business characteristics. However, there are three performance measures, which are manufacturing cost per unit, total sales and part per million (PPM) in defective products shipped to customers, that were adopted by all 10 companies. The most important barrier in Lean implementation is the cultural change since it requires the entire company participation. Finally, the companies participated in this study confirmed that they are satisfy with the result of Lean manufacturing though some companies have not completely adopted the Lean approach into their manufacturing process. To excellent the Lean manufacturing, companies are required to satisfy customer needs, improve the manufacturing process, and increase their flexibility. Furthermore, it is necessary for the top management to provide a clear policies as well as plan and direction. If Lean implementation is to be successful, the communication and human resource department are also the main keys.