Thai tea is traditionally made from either strongly-brewed Ceylon tea or a local Thai tea mixture that often includes ingredients such as star anise, tamarind, and sometimes other spices, which is then combined with condensed milk and sugar.
As for the caffeine content, typically, a standard serving of Thai tea (approximately 8 ounces) can contain anywhere from 20 to 60 milligrams of caffeine. This variability is due to differences in preparation methods and tea leaf types, and could potentially differentiate further for various reasons.