Here's a tip from ImportFood.com:
- Let the wonderful fragrance of Thai iced tea fill your home, and enjoy a stronger-tasting tea. In medium pot boil 8 cups water and add 8-10 heaping tablespoons of Thai tea mix. Reduce heat and let simmer uncovered for 1 hour. Add water to balance and let simmer for additional 1 hour. Add water once again and bring to a boil. Remove from heat. Strain, cool and serve as per above method. This method yields a stronger tea and is the more common way of preparation in Thailand.