Bring the rice, butter, ginger, coconut milk, water and salt to the boil in a saucepan over high heat. Reduce heat to medium-low, cover and simmer until the rice is tender and the liquid has been absorbed, about 20 minutes. Remove from the heat, fluff with a fork and refrigerate until cold.
Heat the groundnut oil in a large frying pan over medium-high heat. Stir in the garlic, shallot, chilli, ginger and lemon grass; cook for 1 minute until the shallot begins to soften. Add the prawns; cook and stir until the prawns have turned pink, then stir in the red pepper. Continue cooking until the prawns are no longer opaque in the centre. Season with basil, fish sauce, soy sauce and lime juice.
Stir the prawn mixture into the chilled rice along with the pineapple and sugar. Sprinkle with coriander to serve.