Fill a pot with boiling water, then add the tea leaves. Cover the pot with a lid, and let the tea steep for 5 minutes For a more traditional tea, use Thai black tea leaves. If you used a tea infuser, simply pull it out. If you used loose tea leaves, pour the tea into a separate pot through a fine, mesh sieve, and discard the loose leaves. Add the sugar first, and stir it until it dissolves. Next, stir in the condensed milk. If you are in a hurry, you can put the pot into an ice bath. Do this by filling a sink with ice, placing the pot into the sink, and then stirring the tea with a whisk while it cools down. Fill 6 glasses with ice, then fill each glass ¾ of the way with tea. If you need to make fewer servings, simply pour the rest of the tea into a pitcher, and store it in the fridge. Evaporated milk is the most traditional, but you can also use whole milk, half-and-half, or coconut milk.

TL;DR in Indonesian:
Seduh daun teh selama 5 menit. Saring daun teh. Masukkan gula ke dalam teh dan aduk, kemudian tambahkan susu kental manis. Biarkan teh dingin hingga suhunya mencapai suhu ruangan (atau lebih dingin). Tuangkan teh ke gelas yang sudah diisi dengan es. Tambahkan susu pilihan Anda sebagai topping sajian.