Make the Hot Thai Tea: Bring loose tea and water to a boil. Remove from heat and steep for 15 minutes. Strain through a fine mesh strainer, then again through a strainer lined with a coffee filter. Let cool to room temperature and then add 1 cup cold 1:1 simple syrup.
Make the Fernet Cream: Combine all cream ingredients in a squeeze bottle and shake vigorously just until the cream starts to thicken.
Make the cocktail: Reheat the tea, pour the hot Thai tea into a glass, add gin, then top with Fernet Cream.