Place 45 grams of loose Thai tea leaves into a teabag.
Place milk, heavy cream, and Thai tea bag in a saucepan and heat until scalded. Set aside and let steep for 30 minutes.
Whisk yolks and sugar in a separate bowl until it’s in the ribbon stage and a light yellow color.
Temper cream mixture into yolk sugar mixture until combined and return to the stove. Continuously stir until thickened or until the nappe stage. Do not go over 180°.
Strain into an ice bath to cool. Chill in the refrigerator until completely cooled.
Place into an ice cream machine and follow the manufacturer's directions.
Transfer the ice cream to the chilled storage container and freeze until hardened to your desired consistency. Alternatively, you can serve it immediately—it will be the consistency of gelato.