Create the Marinade: In a medium bowl, whisk together the pineapple juice, soy sauce, grated ginger, minced garlic, rice vinegar, and sesame oil. Reserve 1/2 cup of this marinade in a separate container and set it aside for the glaze.

Marinate the Chicken: Place the chicken thighs in a resealable plastic bag or shallow dish. Pour the remaining marinade over the chicken, ensuring it is fully coated. Seal or cover and refrigerate for at least 30 minutes, or up to 4 hours.

Prepare the Coconut Rice: While the chicken marinates, thoroughly rinse the jasmine rice in a fine-mesh sieve under cool running water until the water runs clear. In a medium saucepan, combine the rinsed rice, canned coconut milk, 1/2 cup water, and salt. Bring to a gentle boil, then immediately reduce heat to the lowest setting, cover, and simmer for 15-18 minutes, until the liquid is absorbed. Do not lift the lid. Turn off the heat and let the rice steam, still covered, for an additional 10 minutes before fluffing with a fork.

Cook the Chicken: Heat the vegetable oil in a large skillet over medium-high heat. Remove the chicken from the marinade, allowing excess to drip off (discard this used marinade). Place the chicken in the hot skillet, working in batches if necessary to avoid crowding the pan. Cook for 5-7 minutes per side, until golden brown, caramelized, and cooked through to an internal temperature of 165°F (74°C). Transfer the cooked chicken to a cutting board to rest.

Make the Glaze and Serve: Pour the reserved 1/2 cup of marinade into the empty skillet. In a small bowl, whisk the cornstarch with 1 tablespoon of cold water to create a slurry. Pour the slurry into the skillet with the marinade. Bring the sauce to a simmer over medium heat, stirring constantly, until it thickens into a glossy glaze, about 1-2 minutes. Slice the rested chicken. Serve the chicken over a bed of coconut rice, drizzle generously with the glaze, and garnish with sliced green onions, cilantro, and sesame seeds if desired.