Pour oil into a 10-12 inch frying pan. Place over medium-high heat until oil just starts to smoke, about 2 minutes. All at once, add ginger, shallot, chilies, and coriander. Stir for 30 seconds. At once, add rice vinegar, soy sauce, and oyster sauce. Boil, uncovered, over high heat until sauce is reduced to 1 cup, about 1 minute. Let cool.