Run a wedge of lime around the edge of your glass, then press the glass into a shallow dish containing coarse salt to coat the rim in salt.
Add the Thai basil leaves to the bottom of the glass and muddle until they are well broken down.
Combine the tequila, lime juice, agave syrup, and Thai bitters in a cocktail mixer filled with ice and shake until combined. Pour into the glass and garnish with a slice of lime and sprig of Thai basil. Enjoy!