put sugar in small heavy-bottomed saucepot and add 2 tablespoons water to form a wet sand consistency. Cook over high heat until sugar turns a pale golden color, about 5 minutes total. Immediately add vinegar (mixture will bubble rapidly).
Add fish sauce, pepper flakes, and garlic, and cook, stirring with a whisk until reduced to 1/2 cup and mixture is slightly syrupy.
Remove from heat and allow to cool.
Add lime juice and chives. Store sauce in covered container in the fridge for up to 2 weeks.
Place shrimp flat on cutting board, leg-side down and press down until it lies flat and straight. Insert a wooden skewer from the tail to the head. Shrimp should be as straight as possible on skewer.
Set up a breading station: Put flour in one shallow dish, beaten eggs in second, and combine panko, sesame seeds, pepper, 1 teaspoon salt, and 1/2 teaspoon black pepper in third shallow dish. Working one skewer at a time, dredge lightly in flour and shake off excess. Dip in egg and turn until evenly coated.
Place in bread crumb mixture and press with bread crumbs until well-coated. Repeat with remaining skewers.
Heat oil in a large wok or Dutch Oven over high heat until it registers 350 degrees on an instant-read thermometer.
Add shrimp and cook, flipping and agitating regularly until golden brown and crispy and shrimp is cooked through.
Transfer shrimp to paper-towel lined baking sheet and turn to blot out oil. Season with salt. Wipe skewers with clean paper towel.
