In a cup, mix together the coriander, turmeric, cayenne, and ½ teaspoon of the salt. Sprinkle the mixture evenly over the chicken.
Heat a large, deep nonstick sauté pan on medium-high. Coat the chicken all over with cooking spray and add it to the pan. Cook until the thighs are lightly browned, 4 to 6 minutes per side. Remove them to a plate.
Reduce the heat to medium and add the onion and pepper. Cook until the vegetables are soft but not browned, 4 to 5 minutes. Stir in the shallot, garlic, and ginger and cook for 1 minute. Add the coconut milk and then whisk in the brown sugar and 1 teaspoon of the curry paste. Taste the sauce, and add more curry paste and the remaining ¼ teaspoon of salt if desired.
Return the chicken and any accumulated juices to the pan. Bring the mixture to a simmer on medium; then reduce the heat to low and simmer gently until the chicken juices run clear (165ºF internal temperature), 15 to 20 minutes. Divide the chicken and sauce among plates and sprinkle on the basil.
Tip: If you overdid it on the spice, stirring in a bit of half-and-half or milk tames the flames. Casein, the protein found in milk, dissolves capsaicin, the compound that makes peppers spicy.