Too much milk can make the pudding thin and runny. You may also be using the wrong rice. Short-grain rice, also known as pearl, round or pudding rice, contains more starch than long- or medium-grain rice so that it absorbs a large quantity of liquid and becomes quite sticky and very soft.
To enrich the mixture, replace some of the milk with the same quantity of fresh cream, and dot 2 teaspoons of butter over the top before baking. You will also achieve a creamier result if you stir in the skin 30 minutes into the cooking time, and again about two-thirds of the way through.
** Asian Recipes