Make the fish sauce caramel. In a saucepan, combine sugar and 1⁄4 cup water and bring to a low boil. Stir until sugar is dissolved, then allow to cook undisturbed over low to medium heat until a deep caramel color forms, about 20 minutes. You’ll want the sauce to coat the back of your spoon, but be slightly thinner than a traditional caramel. This is more of a sauce texture. Remove the saucepan from the heat and whisk in the fish sauce and remaining 1⁄4 cup of water. Return to medium heat, and stir until the caramel is dissolved. Pour the sauce into a heatproof bowl and let cool completely. Reserve remaining sauce in a Mason jar and refrigerate for up to a week.
Make the fish. Debone and slice the fish into 5 or 6 bite-size pieces per side. Separate the bones and set aside. In a mixing bowl, whisk together rice flour and water until flour dissolves. This will be your fish batter. Fill a deep-fry pot with the oil, and bring to 350°F, keeping this heat consistent throughout the frying process. Dredge the fish in the flour mixture, then drop one piece at a time into the oil, using tongs to keep them separate (so they don’t become one big chunk). Fry for 3 minutes, or until golden brown, then remove. Dredge the fish skeleton in the batter and fry until crispy and golden brown, about 5 minutes. Place fried fish and bones on a paper-towel-lined plate or a draining rack, and set aside.
Dress the fish and plate. In a mixing bowl, toss fried pompano chunks, lemongrass, shallot, jalapeño, ginger, Thai chilies, lime, peanuts, and 6 tbsp. fish sauce caramel. Put fried bones on a large platter, brush with about 2 Tbsp. fish sauce caramel, and add the fried pompano chunks and herbs. Top with fried shallots and serve with fresh lettuce and betel leaves.