The area was proclaimed a national park on 14 May, 1979. According to legend, King Taksin the Great, during a stop on Tak on his way to launch the second attack on Chiang Mai, led his troop to save the Mon people who came to give their allegiance to him from the pursuing Burmanese soldier. He got separated with his troops in a dense forest.

As it was already night-time and difficult for the troops to track their King, they stopped in the forest. Suddenly, a beam of light rose into the sky and neighs of a battle horse were heard. the troops hurried to that point and found their king on his mount in the middle of a stone terrace, Lan in Thai, with shining radiance around his body and surrounded by crouching Burmese soldier.

The dawn was breaking at that time and the Thai word for dawn is “Sang”. This is how the area derived it’s name.