I've generally had good luck finding this at Asian grocers... It can be used as the base for the kind of Thai tea you get from a restaurant, just add sweetened condensed milk. I'm not a huge sugar fan so I drink it straight. Even then, it has a nicely bold flavor, and an incredibly high caffeine content.
Well like I said, I don't care for sugary tea so I have it straight. I use about four heaping tablespoons of leaves for a half gallon of water, which makes it come out strong and rich. Sweetened condensed milk is syrupy, and I did mix it one time years ago, and you only use a small amount. That stuff is concentrated, so don't think of it like how the British put milk in tea... a little bit goes a long way.
Oh my bad, my reading comprehension seems to have stopped at "sweetened condensed milk". Thanks for the tips though, appreciate it!