In a large pot or Dutch oven, heat a drizzle of oil over medium heat. Sauté the sliced onion until translucent, about 3-4 minutes.
Add the minced garlic and grated ginger, stirring for another 1-2 minutes until fragrant.
Stir in the red curry paste and cook for a minute to enhance its flavor.
Add the chicken thighs to the pot and sear them on both sides until lightly browned, about 4-5 minutes.
Pour in the coconut milk and chicken broth, then stir in the fish sauce, lime juice, and sugar. Mix well to combine all ingredients.
Bring it to a gentle simmer, then cover and reduce the heat to low. Let it braise for about 30 minutes, or until the chicken is cooked through and tender.
In the last 10 minutes of cooking, add the sliced bell pepper to the pot, stirring to combine.
Taste and adjust seasoning with salt and pepper as needed.
Serve the coconut milk braised chicken over cooked jasmine rice, garnished with fresh cilantro for a pop of color and flavor.