Make the marinade paste by pounding together the coriander root or cilantro stems, garlic, and peppercorn in a mortar. If you don’t have a mortar and pestle you can use a small food processor or crush well in a thick plastic storage bag with a wooden rolling pin. You want it all to break down into a paste.
Put pork slices, the paste, and the rest of the ingredients, through the baking soda, into a bowl and mix well.
Cover and let marinate in the refrigerator for 3-4 hours.
Thread the pork onto skewers and grill, on medium heat, on your grill, a grill pan, or in a non stick skillet, until slightly charred on both sides and cooked through.
As you are cooking, brush some additional coconut milk/cream on the pork occasionally to keep it moist.
Plate and garnish with some chopped green onions or cilantro leaves.
Serve with dipping sauce. To make the spicy dipping sauce just mix well all the dipping sauce ingredients (from fish sauce to Thai coriander) above, no more than 15 minutes before you eat.