Put the Thai tea mix in the filter and place the filter over a cup.
Pour the boiling water into the cup through the filter. Move the filter up and down a bit to extract the flavor of the tea. Let the tea steep for 2-3 minutes before discarding. If you're using a fine-mesh strainer for this step, simply pour boiling water into your tea and let steep for 2-3 minutes before straining. **Do not steep the tea for too long or it will taste off (best not to go over 5 minutes).
Add sugar, sweetened condensed milk, and evaporated milk and mix with a spoon.
Taste-test the tea and see if you need to add more of anything. You want the tea to be sweeter than you like because the ice will dilute it later.
Fill a glass with ice, pour the tea in, and drizzle some more evaporated milk on top.
If you make this drink in a large amount, it will keep in the fridge (ideally in a bottle or anything with a lid) for about 2-3 days.