Start by making the simple syrup. Add the water, sugar, and thyme to a medium saucepan and bring to a boil, stirring until sugar has dissolved, 2-3 minutes. Add the blueberries and continue to simmer until they have broken down and the sauce begins to thicken, about 10-15 minutes. Let cool slightly then strain into a jar, pushing down on the blueberries to release as much of the simple syrup as possible.
Add sugar to coat the bottom of a small plate, then use a lemon wedge to wet the rim of 2 glasses. Press the rims of the glasses into the sugar to coat.
Add 3 ounces blueberry and thyme simple syrup to the bottom of each glass, then fill each glass about ⅔ of the way with crushed ice. Add 1 ounce lemon juice and ½ ounce maple syrup to each glass. Top each off with seltzer, then garnish with blueberries and thyme.
