Using a mortar and pestle, pound the curry paste ingredients into a fine paste.
Heat the coconut milk in a pot until the cream separates from the milk. Ladle the separated fat from the coconut milk into a wok and fry the curry paste until fragrant.
Stir in the sugar and then add the pork. When the pork is browned, add the remaining coconut milk. If during the course of the cooking the liquid evaporates too much and the curry is too dry, add the meat stock as necessary.
Add the tamarind and lime leaves and stew the pork until it is tender. Season with fish sauce.
Right before serving, add the pak boong or spinach. Place the curry in a large bowl and pair with steamed jasmine rice.