Water is a critical resource for human life, agriculture, and industry, yet Thailand continues to face recurring challenges such as floods, droughts, and water pollution, which highlight the urgent need for an integrated and sustainable water management system. This study aims to examine water management, the central legal framework governing water allocation, utilization, development, maintenance, restoration, conservation, and water rights (Water Resources Act, B.E. 2561. 2018). The research also seeks to identify gaps in the current legal measures and propose guidelines for sustainable water resource management in Thailand. The research used a documentary methodology, which involved a systematic analysis of key legal instruments, government strategic plans, and relevant academic literature on water resource governance and policy implementation. Despite the Water Resources Act introducing crucial mechanisms, such as water licensing systems, usage fees, and avenues for public engagement through water user organizations, the study found that significant operational challenges persist. These issues specifically include the ambiguous roles and overlapping responsibilities among governmental agencies, a strong tendency toward centralized decision-making, and insufficient economic incentives to encourage efficient water consumption. The findings underscore the critical need to embed strong governance principles and ensure genuine community involvement to enhance both the legal effectiveness and the long-term sustainability of the sector. For Thailand to achieve enduring water security, the immediate focus must be on fortifying existing legal frameworks, accelerating the enactment of essential secondary legislation, and cultivating participatory governance. Ultimately, raising public awareness of the actual value of water and instituting market-based incentives for responsible use are vital steps toward sustainable water resource management.