Drain the rice and put into a hot wok or pan. Stir in the coconut milk, salt and sugar. Bring to the boil and leave this to boil softly for about 5-6 minutes or until the coconut milk is absorbed and the rice is thick and sticky. Stir the oil through. Transfer the mixture to a leaf and let cool. The rice will not be cooked properly at this point, so not to worry!
Soften the banana leaves by holding them above a flame for a brief minute or so (you can also steam them or put into the microwave) Place on bananaleaf on the counter and put a tablespoon of rice on top. Add a bit of banana followed by an extra tablespoon of the sticky rice. The banana will be sort of wedged in the middle. Fold the edges of the banana leaf around it like you're making a parcel.
Continue with the rest of the rice, banana and leaves. If you've softened them enough you won't need anything else to keep the leaves in shape.
Fill a steamer with water and bring to the boil. Steam the parcels (fold down) for about 30-35 minutes.