As you know when the supplier produce 16-20-0+x%Sulphur, they using Amsul as raw material.
For 16-20-0 without Sulphur, they using Ammonium Chloride instead of Amsul.
Ammonium Chloride causes of alkaline or saline soil problem.
So, that why Chiatai, ICP, Terragro. TCCC, Worldfert, need 16-20-0 + X%Sulphur. ( which is X=12-14% ).
I bet it should not be successful in Thailand if you insist to promoting for 16-20-0 without Sulphur.
FYR, YVP have been selling 16-20-0 with Sulphur for long time and they just beginning to promote 16-20-0 without from us.