Pour oil into a 1-12" 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 3 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.