Start by mixing the dressing ingredients together. If you are starting with a hard block of palm sugar, you may need to finely slice it or microwave it with a few drops of water to help it dissolve into the other ingredients.1
Next prepare all of the herbs. The lettuce, cilantro, and mint can be coarsely chopped or left whole if the leaves are small enough. The thick outer layers of the lemongrass should be peeled away and only the tender, bottom ⅓ of the stalk should be used. Slice the lemongrass, shallots, red onion, and red peppers very finely. If you are using makrut lime leaves, use a chiffonade cut to slice them finely.
Peel and devein the shrimp. Brush a bit of oil on both sides and then grill them until they're cooked through (2-3 minutes, depending on the size of your shrimp).
Combine the herbs and lettuce in a large bowl and add the dressing. Start by adding half of the dressing, then add more depending on your taste preferences. Finally, add the grilled shrimp while they are still hot and toss everything together. Enjoy immediately!
Notes
1: The dressing can be saved in the refrigerator for several days, if you are preparing the salad ahead of time.