Cut the chicken thighs into 1-inch cubes. Place in a bowl.
Cut off the stem of the chili, slit lengthwise and scrape off the seeds and chop. Leave the seeds on if you prefer spicier satay.
Bruise the lemongrass by pounding the stalks a few times with a pestle or the side of a cleaver. Chop.
Place the chili, garlic, onion, lemongrass and liquid seasonings in a blender and process until pasty. If you don’t have a blender, finely chop the solid ingredients, transfer to a mortar, pound and grind with a pestle until mushy then mix with the liquid ingredients. Stir in the freshly ground pepper.
Pour the marinade over the chicken, mix — with your hand preferably — working the marinade into the meat. Cover the bowl, place in the fridge and let the chicken marinate for several hours or overnight.
Thread four to five pieces of chicken per skewer. Grill for about four minutes per side. Serve with nuoc mam pha.