In a small bowl, combine the coconut milk, soy sauce, sugar, and ½ teaspoon kosher salt.
Place a wok or skillet over medium-high heat. Add olive oil and heat for 30 seconds. Add red pepper flakes, zest, garlic, and curry powder and stir-fry until fragrant, about 15 seconds.
Add the coconut-milk mixture and bring to a boil. Cook until the sauce thickens slightly, 1½ minutes. Add basil. Pour into a bowl.