1. Whisk together the chile pepper, garlic, lime juice, fish sauce, oil, brown sugar and shallot in a large mixing bowl until combined. Reserve 1/2 cup of the vinaigrette separately.
2. Add the watermelon, mango, peaches, cucumber, Thai basil and mint to the bowl with most of the dressing; gently toss to coat. Scatter the peanuts over the surface of the salad and serve with the reserved dressing on the side.