https://www.amazon.com/gp/product/B00SWXO314/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

This is what you want. Google "How to make Thai Iced Tea" and the top articles will say "buy this stuff"

I got a bag earlier this year, and I keep a pitcher of sweet red tea in my fridge at all times. Just add milk for that amazing orange/pink color. I haven't been able to find that stuff in Chinatown or any other areas, so Amazon will probably be your best bet