Whisk together pineapple juice, soy sauce, brown sugar, minced ginger, and minced garlic in a bowl.
Heat vegetable oil in a large skillet over medium-high heat.
Add chicken thighs to the skillet and sear for 6-8 minutes per side until the internal temperature reaches 165°F (74°C).
Remove chicken from the skillet and set aside on a plate.
Pour the pineapple juice mixture into the same skillet and bring to a gentle boil.
In a small cup, combine cornstarch and water to create a slurry, then whisk it into the boiling sauce.
Reduce heat to medium and simmer for 3-5 minutes until the sauce thickens into a glaze.
Stir in the fresh pineapple chunks.
Return the chicken thighs to the skillet, spooning the glaze over them to coat thoroughly.
Garnish with sliced green onions before serving.