A fault plane is on the south of a small isolated Khao To Ngai mountain about 7 kilometers from La-ngu District. It can be seen on a cliff at the seafront accessible by a walking bridge from the national park office. This fault plane site is an important geological structure of the Satun Geopark.
Cambrian red sandstone (Tarutao Group) which is overlain by Ordovician limestone (Thung Song Group) as a normal fault contact boundary between the two rock groups with different ages located on the high cliff with the seafront spanned up to the sea horizon far away. A walking bridge built by the Mu Ko Petra National Park is paved encircling the mountain along the seafront named the “Time-bounded crossing bridge”. The Satun Geopark together with Mu Ko Pethra National Park and Satun Province have launched a concept of group wedding ceremony across the time-bounded location. This is to make a story for local people in learning about the geological site with tourism industry stimulation. The site is thus a tourist spot with inheriting the group wedding tradition.