Cook and stir coconut in a dry skillet over medium-low heat until toasted and fragrant, 3 to 5 minutes. Set aside.
Cut top and bottom off the pomelo, about 1/2 inch from each side. Make vertical cuts around the fruit, about 1/2 inch into the rind. Pull off slices of rind. Pull off any thick pieces of membrane. Split fruit open and separate into segments. Peel membrane off each slice.
Place pomelo slices in a shallow bowl. Sprinkle toasted coconut, peanuts, shallots, and mint on top.
Combine hot water and palm sugar in a jar. Stir until sugar dissolves. Whisk in lime juice, fish sauce, and chile pepper. Spoon dressing over salad.