In a medium saucepan, combine the Thai tea mix, whole milk, and half a cup of heavy cream over medium-low heat. Stir gently as the mixture warms for 5-7 minutes.

Once the tea has steeped and is aromatic, remove it from heat and let it cool slightly for about 2 minutes. Strain the mixture into a bowl.

In a separate bowl, whisk together the strained tea mixture, sweetened condensed milk, and vanilla until smooth and creamy.

In a chilled bowl, whip the remaining heavy cream with an electric mixer until stiff peaks form, approximately 3-4 minutes.

Gently fold the whipped cream into the tea mixture in batches until combined.

Transfer the mixture into a freezer-safe container, cover tightly, and freeze for at least 8 hours or overnight.

When ready to serve, let the ice cream sit at room temperature for 10-15 minutes before scooping.