Heat oil in a large skillet or saucepan, then saute 4 tbsp curry paste until fragrant. Slowly whisk in coconut milk, then fish sauce and brown sugar. Bring to a simmer, then taste for flavour and spiciness and add remaining 2 tbsp curry paste if needed. Add scallops and simmer until just opaque, about 4 minutes, flipping once halfway through.
To make corn relish, heat oil in a small saucepan over medium heat. Add corn, and cook just to warm through. Stir in remaining ingredients and serve over scallops.