Thailand has to seek for new measures to enhance the ability of controlling water in order to mitigate problems of floodwater and lowering of the water table. These problems have tended to make serious threats to Thai people during the last decade. Fortunately, physical characteristics of the country's natural groundwater basins are helpful for orchestrating the conjunctive management of surface water and groundwater. Several studies in Thailand indicated that the implementation of conjunctive uses is possible, and should be emphasized for agricultural areas. However, the conjunctive management approach would certainly require multi-purposes of reservoirs, and then it needs to be accomplished by reservoir re-operations. Other findings based on several studies elsewhere reaffirmed that most major reservoirs can be re-operated to reduce flood risks, prevent or slow groundwater depletion, and buffer the effects of climate change. The great benefits of the conjunctive management are getting more and more attractive to Thai water managers. The reason for this is that even a single large reservoir is very difficult to build due to environmental concerns. Restoring water in subsurface reservoirs is possible, applicable, and useful. The feasibility investigation of re-operation of reservoirs in conjunction with groundwater systems for flood mitigation and avoiding groundwater depletion should be carried out for the first time in Thailand. In addition, Thai water-related agencies regarding irrigation water, surface water, and groundwater should have a logical connection under one umbrella ministry-level organization. Both are substantial steps which must be taken to move towards sustainable conjunctive management.