To prepare the pork, combine the soy sauce, ginger and red pepper flakes in a large bowl. Add the pork pieces and toss to coat completely. Marinate the pork in the refrigerator for up to 6 hours.
In a large sauté pan over medium high heat, add the oil and stir fry pork until it is lightly browned. Remove the pork pieces from the pan and set aside.
Add the pepper and onion to the same pan and saute over medium-high heat until they are tender-crisp, about 5 minutes. Add the garlic and cook for 1 minute before stirring in the coconut milk and salt. Bring the contents of the pan to a boil, then reduce the heat to a simmer. When the mixture is simmering, add the spinach, pears and sugar and continue cooking, stirring frequently, until the spinach wilts, about 5 minutes.
Return the pork to the pan to reheat. When it is hot, remove the pan from the heat and stir in the lemon juice. Serve immediately, with hot rice.