In a large skillet or wok, heat 1 tablespoon of vegetable oil over medium-high heat. Add the diced Spam and cook until it becomes crispy and browned. Remove Spam from the skillet and set aside.
In the same skillet, add the remaining 1 tablespoon of vegetable oil. Add the diced onion and minced garlic, and cook until the onion is translucent and fragrant.
Add the frozen peas and carrots to the skillet. Stir and cook for about 2-3 minutes, or until the vegetables are heated through.
Push the vegetables to one side of the skillet. Pour the beaten eggs into the empty side and scramble until fully cooked.
Add the cold, cooked rice to the skillet. Break up any clumps and mix thoroughly with the vegetables and eggs. Add the cooked Spam back into the skillet.
Pour in the soy sauce, oyster sauce (if using), and sesame oil. Stir well to combine all the ingredients. Adjust seasoning with salt and pepper to taste.
Stir in the sliced green onions. Cook for an additional minute, then remove from heat.
Enjoy your meal!