Preheat the oven to 400 degrees. Drain the pineapple juice from the can to use in the sauce (it should be about 3/4 cup juice total). Save the pineapple chunks for later. Combine the pineapple juice, grated ginger, minced garlic, soy sauce, rice vinegar, brown sugar, and cornstarch in a small sauce pot. Stir until everything is well combined and the cornstarch is dissolved. Cook the mixture over medium heat until it begins to boil and becomes thick and glossy. Turn the burner off and add the pineapple chunks to the sauce.
Coat a small casserole dish with non-stick spray. Arrange the chicken thighs in the dish so that they are not overlapping. Pour the pineapple teriyaki sauce over the chicken, allowing some to get under the chicken pieces.
Bake the chicken in the preheated oven for 35 minutes, or until the chicken is cooked through. Top the chicken with the sliced green onions. To serve, scoop one chicken thigh plus pineapple pieces and sauce over a bowl of cooked rice.