Rattanai Reservoir is a small irrigation project under the royal initiative. It has a capacity of approximately 2,020,000 cubic meters, located on an area of 1,600 rai, with a 15-meter-wide overflow drainage building, and the soil embankment, 15 meters high and 250 meters long. Construction was completed in 1987. It is useful for consumption and agriculture. The reservoir is similar to a lake, suitable for recreation for tourists, and it is the most beautiful viewpoint of Khao Kho District.