Ko Tachai on Google Earth - Similans National Park it is a long way north of the main islands (1 to 9) - 47km from the northen-most island #9, 60km from the Surins NP Headquarters at island #4, 27 km from Ko Bon and 70km from the Similans mainland departure port at Thap Lamu south of Khao Lak. The Surins are a lot closer than Similans 1 to 9 - 37km. To travel here is just open in this last 4 years for toursit can visit and spent time on the Island but only Day Trip program