Place prawns in mixing bowl and squeeze lime juice on top; toss to coat prawns evenly.
Heat butter in a large pot and sauté the capsicum with shallots for 2 to 3 minutes. Mix in corn, okra, tomatoes, tomato purée, thyme, bay leaf and chilli. Season with salt and pepper and simmer for 10 minutes.
Add the prawns, return to a boil and simmer for another 5 minutes. Remove bay leaf and chilli before serving.