Amnat Fongchai, head of the sanctuary, said the two-month closure will allow natural resources to recover during the rainy season.
The waterfall will be off limits for leisure visits and study tours during the two-month period, he said.
Thi Lo Su is a limestone formation 900 metres above sea level located within the Umphang Wildlife Sanctuary.
Umphang Wildlife Sanctuary, Thung Yai Naresuan and Huay Kha Kaeng Reserves, as well as Khlong Lan and Mae Wong National Parks form Thailand's largest wildlife haven and Southeast Asia's top virgin forest, according to the Tourism Authority of Thailand.
Tak's Umphang district sees a decline in tourists during the rainy season every year as heavy rains make access to many natural attractions difficult.