Trim the tuna and dice into equal pieces.
Whisk together the soy sauce, brown sugar, sesame oil, vinegar, garlic, ginger, and green onion in a bowl. Add the tuna and toss to coat. Cover and refrigerate for at least 30 minutes.
While the tuna marinates, make the sriracha aioli: Whisk together the mayonnaise and sriracha in a small bowl.
Make the crispy wonton chips: Pour oil to a depth of 1 inch in a Dutch oven and heat to 325°F. Add the wontons, a few at a time, and fry in batches about 30 seconds on each side or until golden brown. Drain on paper towels and sprinkle with salt while still hot.
To serve, arrange the wonton chips on a serving platter. Top with the ahi poke, cucumber, avocado, and seaweed salad. Drizzle with the spicy mayo and eel sauce. Garnish with more green onions, if desired. Serve immediately.