Geography
Nam Nao covers the border between northeastern and northern Thailand. Its particularly part of the Phetchabun mountainous range running through Chaiyaphum and Phetchabun provinces. Phu Phajit mountain is the tallest in the Park and topography comprises evergreen forests and streams. There are many rivers and streams within this important watershed area Pa Sak River is one of these, it eventually joins the Chao Praya River, others are Pong and Loei rivers and Khon Kaen and Nam Churn streams. All these flow into the Ubonrat Dam.