The path leading to Hup Khao Pa Tat is quite dark, so bring a flashlight with you, those provided by the park are not always very powerful. After walking, not very long after the entrance, you will come to the famous big hole through which the light enters on the ancient palm trees. This is the iconic image here.
The main element that made the reputation of Hup Pa Tat, the partly collapsed cave, was discovered by chance by the monk Phra Khru Santithamma Kosol (Luangpho Thongyot), abbot of the nearby Wat Tham Thong temple in 1979. He found there a lot of Arenga Pinnata, ancient trees close to palm trees. They gave the place its name since in Thai, they are called tat while pa means forest, and the word hup refers to the chasm formed by the cave with its collapsed ceiling. The access to the cave was then simplified in 1984 by digging a 70-meter passage that visitors still use today. Legend says that the monk dug it himself but I imagine he was helped ;). Later, the Ministry of Forests declared Hup Pa That a preserved area due to its incredible topography and the rare plants you can find there.
Note that among the wild animals living in Hup Pa Tat, there are elongated turtles (Indotestudo elongata). You may be lucky enough to see some if you are attentive.