In a small bowl, whisk together fresh lime juice, sambal oelek, finely grated fresh ginger, fish sauce, and finely chopped scallions. Add the finely sliced serrano chile.

In a large mixing bowl, gently stir together seedless watermelon chunks and ripe peach slices.

Pour the prepared dressing over the fruit mixture, gently tossing to coat.

Serve immediately, garnished with fresh basil leaves and dry roasted peanuts.