I am currently in Langkawi and have been busy shopping! Things are definitely cheaper here, and some items are GST-free. Obviously, one has to shop smart.
For instance, when in Langkawi, it is better to buy imported chocolates than locally-manufactured ones. Even though the nett price of local chocolates is cheaper than imported ones, buying the imported chocolates here is cheaper than buying in other cities, or airports because this is a duty-free island. However, one has to spend at least two nights on the island before qualifying for the duty-free items.
I am checking out today and flying home later in the afternoon. I wonder if there's still be opportunity for me to spend. Hoho! Third island vacation within a month, I am broke and super tanned.