Wash the rice by placing it in a mixing bowl, covering it with cold water, and swishing gently. Pour off the cloudy water and repeat until the water runs mostly clear. Soak the rice for at least 4 hours or overnight.

Drain the soaked rice and line a steamer rack with a moist muslin cloth. Place the rice on the cloth and steam over rapidly boiling water for about 20-25 minutes, until tender yet chewy.

Stir the rice flour into water until smooth. Combine it with coconut milk and salt in a pot. Cook over medium heat, stirring constantly until it comes to a gentle boil, then remove from heat and let cool.

Rinse the mung beans well, cover with water in a small pot, and bring to a simmer. Remove from heat, cover, and let sit for 10 minutes. Drain, dry thoroughly, and toast in a lightly greased sauté pan until crunchy.

In a new pot, mix sugar, coconut milk, and salt together. Heat until bubbling and fragrant, then pour over the cooked rice and let it sit for about 20 minutes to absorb the syrup.

Serve the sticky rice beside fresh mango slices, drizzle generously with the salted coconut sauce, and top with crunchy mung beans.