Preheat oven to 375°F.
In stockpot over high heat, bring water to a boil. Add rice. Stir. Return to a boil. Reduce heat. Cover and simmer until rice is tender and liquid is absorbed, 18 to 20 minutes. Remove from heat. Let stand 10 minutes. Fluff with fork.
While rice is cooking, on a sheet pan coated with cooking spray, place chicken in single layer. Coat chicken with cooking spray. Bake until internal temperature reaches 165 F and juices run clear, 12-15 minutes. Cool. Dice into small pieces
In sauté pan or wok over high heat, heat oil. Add chicken, garlic, and ginger. Stir-fry until browned, 1-2 minutes.
To serve, fill each lettuce leaf with ½ cup of rice and ½ cup of chicken.