It does happen, but in a protracted way. Wolf Blass, Cabernet Sauvignon, Lellow label which I had never bought under 599, can be had at 569, in many shops. There are lot of wines now in the 500 to 650 range a lot more than before; interestingly many of these are new labels, which I have never seen before in Thailand.
IMHO, the retail prices are [in the process of] dropping by 5 to 10%. It is also a question of stock rotation, so good wines of 1000/1200 THB which are selling less will probably follow once they get reimported.