Bring a large pot of water to a boil. Slowly add desired amount of tapioca pearls. Bring water back up to a simmer and cook about 20 to 30 minutes, stirring occasionally so pearls don't clump together. Rinse pearls in cold water once cooked.
Pour hot water over Thai tea mix and let steep for at least 10 minutes. Allow liquid to cool completely before making drink. Strain tea leaves. Add tapioca pearls, ice, Thai tea mixture and sweetened condensed milk to taste. Stir and enjoy!