I had been anticipating this given the Thai gov't announcements a few months ago regarding doing away with the 1,500 baht vat free threshold on imports.
I placed an order with iHerb on 17 Jul (after notification of the change in arrangments by iHerb) and received delivery on 25 July by Flash Express (with no additional taxes to collect).
The invoice included an all-in amount for duties/vat of 15% that I had prepaid. I usually purchase when iHerb has a promo/discount which I guess offsets the the duties/taxes to some extent.
In the past I have usually ticked the box for delivery by Flash Express (with free delivery) instead of US/Thai Post, and this is now the only option available, which means the max. number of items per order is limited to 3.