My local Thai restaurant waitress told me that there was over 100 milligrams in a standard 12oz glass. That's essentially a Red bull.In summary:"The amount of caffeine in tea depends on a number of factors, including the method and length of brewing or steeping. Studies also show that leaf location on the tea plant affects content of caffeine in that tea. The youngest leaves, highest on the plant, contain the greatest concentration of caffeine AND antioxidants."Since Thai tea us usually made from black tea, we can estimate caffeine content based on typical black tea steeping methods (5 minutes at 212°F) to be around 11mg/oz (132mg for a 12 oz glass). Thai tea is usually brewed strong (1 tablespoon tea per 8oz boiling water) which will raise this caffeine estimate, but also uses evaporated milk and the tea itself contains spices besides the actual tea (leaves of the Camellia sinensis plant), which could lower this estimate.