Hmmm, careful in thailand. Learn clearly what the laws there are, the penalties are extremly severe.
There are rewards for information on people carrying contraband, so it isn't unheard of for a thai to sell you something, then turn around and sic a cop on you to collect the reward (double paycheck). This includes the pharmacies.
I would forget about the roids, and buy some nice designer knockoffs (take an empty bag, or buy another there, the shopping is AMAZING), enjoy the people, the food, the beach, and the party.