In a large bowl, combine chicken thighs with soy sauce and 2 tablespoons of cornstarch. Cover and marinate for 30 minutes.

In a small bowl, mix lemon juice, sugar, water, cornstarch, and lemon zest. Stir until sugar dissolves and set aside.

In a separate bowl, combine flour with remaining cornstarch. Toss marinated chicken in the flour mixture until coated.

Heat oil in a deep pot to 350°F. Fry the chicken in batches for 4-5 minutes per side until golden brown. Drain on paper towels.

Pour the sauce over the fried chicken and cook for an additional 2-3 minutes until sauce thickens.

Serve immediately over steamed jasmine rice or with stir-fried vegetables.