For the quail eggs, you can use fresh or canned, a shortcut for perfect hard boiled quail eggs is in the Recipe Notes section. If using canned eggs, and there is nothing wrong with that, just drain the eggs needed and refrigerate the rest.
Once you have the hard boiled quail eggs sorted out, fresh and peeled or canned, cut each in half lengthwise.
Heat a non stick pan to medium heat with about ½ inch of cooking oil, when hot, add the egg halves, fry until lightly browned on both sides, remove the eggs to a serving plate.
Pour out all but 1 tablespoon of oil, easy way is to pour out all hot oil into a jar and add 1 tablespoon of oil back to the pan.
Heat the oil and when hot, add the chilies and garlic, and cook until fragrant, about 1 minute. Turn the heat down to medium.
Add the soy sauce, fish sauce, sugar, and vinegar and cook, stirring, until the sugar caramelizes and the sauce thickens and turns brown.
Pour sauce over the eggs, sprinkle with the onion and coriander, serve, and enjoy.