Ice Coffee, along with Ice Tea is very popular in Thailand.
The best, if you can find it, is still made the old fashioned way, filtered through a "sock".
Here in Hang Dong, just on the outskirts of Chiang Mai is "The Coffee Lady" who makes the best Iced Coffee around.
She'll customized it any way you wish (less sugar, more condensed milk, or whichever way you take your coffee) and always with a huge smile.
Her sidekick is always around helping, but rarely smiling.