In a bowl, combine the chicken thighs with 3 tablespoons of the soy sauce, 1 clove of minced garlic, and half the grated ginger. Marinate at room temperature for 20 minutes, or refrigerate up to 4 hours.
In a small saucepan, whisk together the remaining soy sauce, brown sugar, pineapple juice, remaining garlic, and remaining ginger. Set aside.
Heat sesame oil in a large skillet over medium-high heat. Sear the chicken thighs 4–5 minutes per side, until deeply golden.
Pour the sauce mixture over the chicken. Reduce heat to medium-low and simmer uncovered for 8–10 minutes, flipping once, until internal temperature reaches 165°F.
Remove the chicken to a plate. Whisk the cornstarch and cold water together, then whisk into the sauce in the pan. Simmer 1–2 minutes, whisking constantly, until thickened. Return the chicken to the pan and turn to coat in the glaze.
Let the chicken rest 5 minutes, then slice against the grain. Garnish with green onion and sesame seeds and serve over rice.