Heat up the evaporated milk in a saucepan or a pot (do not boil). Add Pantai Thai Tea mix. Let it steep for 30 minutes.
Strain the tea leaves into a large bowl using a sieve. Use the back of a spoon to press out as much liquid from the pulp as possible.
Rinse the pot (wash out the tea mix residue), then put the tea mixture back in to the pot (do not put it on the stove top yet; just set aside)
In a separate medium sized bowl, whisk the egg yolks.Set aside.
Put the pot or saucepan with the tea mixture back on the stove top and turn on the heat to low.
Add the condensed milk and heavy cream to tea mixture. Stir well. Turn off the heat just before boiling (when you start seeing steam coming from the liquid).
Temper the egg yolks: while whisking the egg yolks, use a ladle to slowly pour the tea mixture into the egg yolks. Repeat a few more times until egg yolk mixture is up to temperature.
Pour the egg mixture back into the pot. Stir constantly over low heat with a wooden spoon or silicone spatula until thick enough to coat the back of the spoon.
Pour into ice cream maker.
Let it sit in the freezer for at least 6 hours before serving.