Heat the cooking oil in a pan. Add the pork strips and cook over high heat until the edges start to brown. Add the garlic and onion, stir and cook until fragrant, about a minute. Pour in the vinegar. Let boil. Stir again then pour in the soy sauce. Stir, bring to the boil, add the bay leaf, cover and simmer for 15 minutes.
Meanwhile, prepare the kangkong. Cut into two-inch lengths, separating the lower portion of the stalks from the leaves.
When the pork is done (the liquid would have been reduced by almost half by this time), add the kangkong stalks. Cover and simmer for two minutes. Add the rest of the kangkong, stir and cook for a minute or just until the leaves are wilted.