To Make Boba:

1. Bring the 6 cups of water to a boil in a deep pot, and add the tapioca. Bring it to a boil again, stir to break up large clumps of tapioca, cover, and turn the heat down to medium low to maintain a gentle simmer. 
2. Cook for 15 minutes, stirring occasionally to prevent sticking. After 15 minutes, turn off the heat, stir one more time to ensure there is no tapioca sticking to the bottom of the pan, and allow it to sit for another 15 minutes.
3. Check the tapioca pearls by tasting one. If it still has an opaque white center, repeat the simmering and holding for another 10-15 minutes, until all the tapioca balls are translucent. 
4. Drain the tapioca pearls and rinse under cold water.
5. If the tapioca pearls still have opaque white centers, repeat STEP 1 and STEP 2 until all the tapioca balls are translucent. You may have to repeat a few times depending on their size.
6. In the meantime, combine ¼ cup sugar with 1 cup water in a small saucepan. Heat the pan over medium high heat until the sugar is completely dissolved, about 3 minutes. Set aside to cool until ready to use.
7. Once the tapioca pearls are cooked, drain and rinse under cold water one more time. Then put them into the sugar water to prevent them from sticking together.

For Thai Tea:

1. Combine the tea leaves and water in a saucepan. 
2. Bring the water to a simmer over high heat, lower the heat to medium low, stir the contents of the saucepan, and cook at a gentle simmer for 10 minutes. 
3. Add the sugar, stir the tea to dissolve the sugar, and cook for another 5 minutes. Turn off the heat and let the tea steep for another 15-20 minutes until the tea leaves sink to the bottom. 
4. Strain the tea into a pitcher and add the ice to cool the tea.
5. Add a couple tablespoons of tapioca to the cup, add a ½ cup of ice, and pour the tea almost to the top. 
6. Add the evaporated milk, stir, and serve with a straw.