Make*very* strong coffee (50-100%% more coffee to water than usual), use something like Cafe Du Monde which has chicory in it. Pour 6-8 oz into cup and add about 1 Tbs sweetened condensed milk. Stir, then pour over ice.
You'll have to experiment with the strength and milk so you get lots of taste after the ice/water dilutes it.
Calls for grinding two or three fresh cardamom pods and putting them in with the coffee grounds. Make a strong coffee with a fresh dark roast, chill it, sweeten and add half-and-half (that's what I saw the chef using at the last Thai restaurant I went to) to taste.
This is a derivation-from-memory of a recipe that I first read some two years or so ago for Thai iced coffee (that lovely stuff that I can drink for hours on end while I'm slurping down panang and pad thai).
Makes 18-cup pot of coffee
Place the coffee and spices in the filter cone of your coffee maker. Brew coffee as usual; let it cool.
In a tall glass, dissolve 1 or 2 teaspoons of sugar in an ounce of the coffee (it's easier to dissolve than if you put it right over ice). Add 5-6 ice cubes and pour coffee to within about 1" of the top of the glass.
To be totally cool, serve with Flexi-Straws and paper umbrellas...
One other fun note: I got a fresh vanilla bean recently and put it to good use by sealing it in an airtight container with my sugar. The sugar gets the faintest vanilla aroma and is incredible in Real Chocolate Milk (TM) and iced coffee.
One final note: this would probably be even better with iced espresso, because the espresso is so much more powerful and loses its taste less when it's cold.