Heat 1 ½ tablespoons of oil in a large skillet over medium high heat. In a large bowl, toss chicken thighs with flour to coat. Brown chicken thighs for 3-4 minutes per side or until golden brown. Remove to plate.
Add ½ tablespoon oil to the same skillet and add red onion and red pepper. Cook for 5 minutes, stirring occasionally.
In a medium bowl, mix brown sugar and cornstarch. Stir in the juice from the canned pineapple, minced garlic, ginger, salt, and pepper.
Add the sauce to the skillet and heat until the mixture comes to a boil. Turn down heat and simmer for 2 minutes or until sauce has thickened.
Return chicken to the skillet and stir to coat with sauce. Cover skillet and cook on medium heat for 10-15 minutes or until chicken is no longer pink inside.
Garnish with green onions and sesame seeds and serve with rice.