As Thailand accelerates its transition toward a low-carbon economy, Battery Energy Storage Systems (BESS) have emerged as a cornerstone for grid modernization. Under the updated Power Development Plan (PDP), BESS deployment is critical to mitigating renewable energy intermittency and securing grid stability. Moving from policy frameworks to aggressive national implementation, Thailand is building a comprehensive ecosystem that integrates utility-scale storage with behind-the-meter industrial installations. Crucially, this roadmap goes beyond mere deployment; it establishes vital foundations for technical standards, grid code compliance, and circular economy practices, including the digital Battery Passport for end-of-life management. Ultimately, this strategic blueprint positions Thailand as the leading hub for energy storage integration in Southeast Asia.