Rattanai Reservoir

Rattanai Reservoir is an irrigation dam in the Khao Kho highlands of Phetchabun province, with a storage capacity of about 2.02 million cubic metres across roughly 1,600 rai. It sits in a basin at around 1,000-1,200 metres elevation, and that basin geography is the whole reason people come: cool overnight air collects and condenses into a fog that fills the valley almost every morning, creating the “sea of mist” that draws Thai domestic tourists to Khao Kho by the busload during cool season. Access to the reservoir area is free, daily 08:00-16:30.

The reservoir itself is functional rather than scenic up close — an embankment dam feeding water to the surrounding agricultural area, not a designed park. What’s worth the trip is the viewing experience around it. The Khao Kho scenic viewpoint on Highway 2196, about 500 metres from the reservoir, is widely rated the best sea-of-mist and sunset spot in the district: arrive at sunrise (roughly 5:30-6:30 AM in cool season) to watch mist fill the basin below while the surrounding peaks stay clear, or come back at dusk to watch the sun drop over the water. Photographers and Thai road-trippers treat this viewpoint as a Khao Kho must-stop rather than the reservoir itself.

That draw has built a small tourism cluster around the water — resorts, homestays, and campgrounds have opened specifically because of the mist and sunset views, ranging from simple tent pitches to small hillside resorts with reservoir-facing rooms. Vendors set up near the main viewpoints on weekends, selling coffee and snacks to the early-morning crowd. It’s a genuinely developed micro-destination within Khao Kho, not an isolated body of water — plan for company if you visit on a cool-season weekend.

Insider Tip: Weekday mornings thin the crowd dramatically. If you can visit on a Tuesday or Wednesday rather than a Saturday sunrise, you’ll get the same mist with a fraction of the tour groups and camera tripods jostling for the same viewpoint.

Rattanai Reservoir anchors a cluster of Khao Kho attractions worth combining into a day: Khao Kho National Park for hiking and its own viewpoints, Khao Kho Royal Palace for the hilltop former residence with panoramic views, and Magic Hill, the district’s well-known optical-illusion road stop. All sit within a short drive of each other along the Khao Kho loop roads.