Combine the lemongrass paste, minced garlic, lime juice, soy sauce, maple syrup, avocado oil, and fish sauce in a small bowl or measuring cup and whisk until smooth.
Place the chicken thighs in a large zip-top bag, pour in the marinade, seal the bag, and massage so all pieces are evenly coated.
Refrigerate and marinate for at least 1 hour, or up to several hours for more flavor.
When ready to cook, preheat the oven to 400°F (200°C). Arrange the marinated chicken and any remaining marinade in a single layer in a large baking dish.
Bake on the center rack for 20 minutes, then switch the oven to high broil and broil for about 5 minutes until the edges are slightly crispy.
Check the internal temperature with a digital thermometer; thighs are safe at 170°F, but many prefer 180–200°F for texture—cook to your preference.
Remove from the oven and serve with your favorite sides.