Pat the chicken thighs dry with paper towels.
In a large bowl, combine all marinade ingredients: lemongrass, onion, garlic, ginger, Thai red curry paste, sweet chili sauce, fish sauce, soy sauce, lime juice, brown sugar, salt, pepper, and olive oil. Stir to evenly combine. Reserve 1/4 cup for glazing while roasting; place in a covered container and refrigerate until ready to cook the chicken.
Add chicken thighs to the remaining marinade in the bowl, ensuring all chicken pieces are evenly coated. Cover bowl and refrigerate for at least 30 minutes, or up to 4 hours for more flavor.
Preheat oven to 400°F. Remove chicken thighs from marinade, allowing any excess marinade to drip off.
Line a rimmed baking pan with foil or parchment paper, and place a rack on top. Place chicken thighs on rack. Roast in the oven, flipping the chicken after 15 minutes. Using an instant-read kitchen thermometer, check internal temperature at the thickest part of the thighs – the chicken will be done when it reaches 165°F. During the last few minutes of roasting, brush chicken with the reserved marinade – the glaze will caramelize a bit as the chicken finishes cooking.
Transfer chicken to a serving platter. Serve hot with your favorite tender, small leaf lettuce and a sprinkling of chopped green onions. Offer lime wedges for individuals to squeeze over their chicken.
