คำถามเกี่ยวกับความสัมพันธ์ข้ามสกุลเงิน EM กับสินค้าโภคภัณฑ์

That's a good observation. I tend to think of it in terms of net commodity exporters vs. importers, and then within exporters, differentiating between those with diversified export bases vs. single-commodity reliance.

You're spot on about the commodity link for BRL and ZAR. For INR, I'd say the capital account openness and domestic institutional flows play a huge role, making it more resilient to pure commodity swings. Have you looked into the "terms of trade" effect for a more structured approach?

BRL and ZAR are clear commodity plays, no argument there. INR is a different beast; you're right about domestic policy and growth, but don't forget the significant oil import bill. That's a huge factor often overlooked.