Rinse leaves thoroughly and rip to release their oils.
Combine the ripped leaves, water, and sugar in a small saucepan and heat over medium-low heat.
Bring the mixture to a low boil, maintaining a medium-low heat to avoid burning the sugar. This will take 5-10 minutes. Stir occasionally to help the sugar dissolve.
Once the mixture has reached a low boil turn off the heat and let cool in the saucepan for 30 minutes.
Place a mesh strainer over the jar you’ll use to store the Thai Basil Simple Syrup and pour the syrup over it to strain out the basil leaves. Let cool completely and store in the refrigerator for up to a month.