The Asian Development Bank retained the services of Global Best Practice Group’s expert as a Water sector specialist to undertake a comparative infrastructure development assessment between South Korea and Thailand. The evolution of water sector planning was traced in both countries and field visits and discussions were held with stakeholders, agencies, government ministries and private sector operators. A comprehensive comparative infrastructure assessment was undertaken to identify service inefficiencies and inadequacies in capacity. Implementable solutions and recommendations were developed based on lessons learned. Areas of improvement and mutual cooperation between the two countries were identified as opportunities for ADB intervention and mutual cooperation and collaboration.