Pour the tequila, cream of coconut, lime juice, and 2 tablespoons of the sugar syrup in a cocktail shaker or large mason jar with a lid. Shake it well to combine everything. Then add in 3 drops of sriracha hot sauce, and shake everything together again.
Dip a spoon in to taste the mixture. There should be just a little heat. If you want more heat you can add more sriracha a drop at a time.
Coat the rims:
Combine the salt and makrut lime leaf powder in a shallow dish (wide enough to fit the rim of your margarita glass into.) Have another shallow dish ready with sugar syrup in it.
Dip the rims of the glasses first in the sugar syrup and then in the salt-lime mixture, dabbing the rim until it has an even coating of salt on it.
Pour the drinks:
Place ice cubes in each glass carefully so you won't knock salt off the rims. Pour the margarita mixture into each glass. Serve the drinks immediately.
Notes
Cream of coconut gives this cocktail sweetness and rich coconut flavor. Look for cream of coconut in the section where drink mixers are kept, in grocery stores or liquor stores. (This is not the same as coconut cream or coconut milk.)
Mix this margarita just before serving. The ingredients tend to separate when made in advance.
Makrut lime leaf powder can be found in spice stores online and in bulk spice sections of natural foods stores. If you don't have any you can use just salt on the rims, or grind salt together with lime zest in a food processor.