Cut the chicken thighs into 2-inch strips and place them in a large bowl.
In a separate bowl, whisk together the beaten eggs, mochiko (sweet rice) flour, cornstarch, soy sauce, granulated sugar, sesame seeds, grated garlic, salt, and chopped green onions until smooth to form the marinade.
Pour the marinade over the chicken strips and toss thoroughly to coat each piece evenly.
Cover the bowl and refrigerate to marinate for at least 4 hours or overnight for best flavor and texture.
Heat about 1 1/2 cups of neutral oil in a deep skillet or Dutch oven to 325°F (use a thermometer for accuracy).
Working in batches to avoid overcrowding, gently add marinated chicken pieces to the hot oil and fry until golden brown and cooked through, about 3–4 minutes per side (internal temperature should reach 165°F).
Remove the chicken with tongs and drain on a rack or paper towels.
Arrange the crispy mochiko chicken on a plate, garnish with extra chopped green onions if desired, and serve with steamed white rice.