Combine the sugar and 1/4 cup water in a small saucepan, bring to a simmer over medium heat and simmer until the sugar dissolves. Turn off the heat and add the fish sauce, lime juice, tamarind concentrate, garlic and chiles. Allow to cool completely. Heat 2 to 3 inches of vegetable oil in a large wok or Dutch oven to 350 degrees F. Make sure there is enough oil to almost fully submerge the fish (it's fine if a little of its body is above the oil because you will be flipping it) but there's still enough room so that the oil will not overflow once the fish is placed in the wok; leave at least 2 inches of space between the top of your vessel and the oil.
Cut three long slits into each side of the fish, making sure to cut down to the bone. If the fish is a little large for the wok you are using, trim its tail as needed to make it fit. Sprinkle liberally with kosher salt (about 2 teaspoons). Put the rice flour into a large baking dish. Dredge the fish in the rice flour, shaking off any extra flour that does not adhere to the fish.
Place the fish into the oil by sliding it down the side of the wok to avoid splashing, and fry until golden brown and cooked through, flipping once, for 6 to 8 minutes. When you are flipping the fish, use two slotted spoons or spatulas (one underneath and one on top of the fish) and gently turn over, being careful not to splash hot oil. A good way to test if the fish is done is to insert a cake tester into the thickest part of the fish and then hold the tester under your lip. If the tester is warm, the fish is done. Transfer the cooked fish to a baking sheet lined with paper towels to catch any excess oil.
In a mixing bowl, toss the cilantro and scallions with 2 tablespoons of the tamarind lime vinaigrette.
To serve, place the whole fish on a platter and top with the herb salad. Spoon vinaigrette over the fish and serve any additional vinaigrette on the side.
If you do not wish to fry a whole fish, you can buy skin-on black bass fillets and shallow-fry them in a pan, following the same method as above.
Recipe courtesy of Susan Vu for Cooking Channel