Finely grate or mince ginger, lemongrass, and garlic into a medium bowl. Add coconut milk, tumeric, grand masala, cinnamon, chili oil (or cayenne mixture), lime juice, brown or coconut sugar, salt, and 2 Tbsp avocado oil; whisk to combine. Add chicken and toss to coat. Let chicken marinate at least an hour at room temperature or overnight in the refrigerator. The coconut milk will harden, but it will melt when heated again.
In a large skillet over high heat, pour in oil for searing—enough to almost coat the bottom. Remove chicken from marinade, and scrape any excess off. Sear the chicken thighs for 2 minutes each side, then pour in the remaining marinade and bring to a boil. After liquid boils, reduce heat to medium-low and simmer the chicken thighs for 25 minutes.
The liquid will reduce in volume and become thicker; use it to top your rice and vegetables. Enjoy!