Place a medium bowl in the refrigerator. Heat 2 to 3 inches of vegetable oil in a small saucepan to 350 degrees F. Fry the wonton wrappers in batches over medium-high heat, until golden brown and crisp, 15 to 20 seconds on each side. Remove the wonton chips with tongs or a slotted spoon and drain on a wire rack set over paper towels; sprinkle with salt. Set aside.
Place the hot water in a small heatproof bowl, sprinkle in the seaweed and let it reconstitute, about 5 minutes. Rinse the seaweed under cold water. When cool enough to handle, squeeze out the excess water with your hands and let drain in a fine-mesh sieve.
Meanwhile, cut the tuna into tidy 1/2-inch (12-millimeter) cubes and transfer to the chilled bowl to keep the raw fish cold. Add the seaweed, onion, sesame oil, chile flakes and soy sauce. Fold very gently with a large spoon, like you're folding egg whites, until the tuna poke is well combined.
Top each wonton chip with about 2 tablespoons of the tuna poke. Garnish with the sesame seeds and scallions and serve right away.