Chop the ends off of the lemongrass, and peel the outer layers. Smash the stalks and using only the bottom 1/3 of the stalk, cut strips.
Add oil to a large saucepan or stock pot and add the lemongrass, onion, garlic, ginger, corn, and peppers. Sauté until softened and fragrant, about 5 minutes.
Add the chicken and cook just until browned, about 1 to 2 minutes.
Add the fish sauce, curry powder, chicken stock, lime juice, and coconut milk. Cover the pot and bring to a gentle boil.
Reduce heat and simmer until chicken is cooked through, about 25 to 40 minutes.
When ready to serve, remove the harder pieces of lemongrass.
Serve with chopped cilantro