Normally all the big forwarding companies (DHL, FedEx, UPS ...) add a 30% tax surcharge for everything above the duty-free allowance entering the kingdom from abroad, no matter what kind of tariff group.
This is the experience of me and my friends.
For articles from Lazada, Gearbest and Banggood I never had to pay tax in the past; they don't use the big forwarding companies.
Never ordered from Amazon.