Oily scalp, like oily facial skin, is due to the overly active oil glands of the skin, which is genetically predisposed and hormonally mediated.
Therefore, shampoos per se can do and help to a certain small extent in controlling the scalp condition you have. Our hot tropical climate definitely will require you to ensure that you do daily shampooing. This will help to manage the oily scalp better. A mild shampoo and the concomitant use of a hair conditioner are recommended for daily use.