Put mung beans into a large container and cover with several inches of cool water. Soak beans for 1 hour.

Drain mung beans and spread them out onto a flat surface. Pat gently with paper towel to blot some of the water; air-dry beans for 15 minutes.

Heat oil in a skillet over medium heat. Cook and stir beans in hot oil until evenly browned and crunchy, about 5 minutes. Drain beans and transfer to a mixing bowl; add chile pepper, green onion, and salt and stir to coat.