Crack the eggs and drain the egg whites and yolks into a small bowl.
Add the fish sauce, light soy sauce, sugar, and MSG to the eggs and whisk the ingredients together with a whisk or fork.
Chop the spring onions into 1cm pieces, add to the beaten eggs, and continue to whisk. Once you combine eggs with the other ingredients in a uniform mixture, set the mixing bowl aside.
Preheat a little oil (or cooking spray) in the frying pan over medium-high heat.
Add the egg mixture to the skillet and distribute evenly over the surface. How much of the omelet mix you fry at a time depends on the surface area of the frying pan. For this recipe, we used our 10-inch cast iron griddle, which could hold about a cup of the egg mixture.
Fry the mixture over moderately high heat for about a minute-and-a-half. Then, lift the omelet using a spatula from the edge of the pan and flip it over. Continue frying until the omelet is golden brown, for a total frying time of 2-3 minutes, then transfer the omelet to a serving dish (feel free to remove excess oil with paper towels, if needed).
Repeat steps 5 and 6 with the rest of the omelet mix, adding cooking oil or cooking spray as required.
Place the omelet onto a serving plate and eat with white rice and the Cambodian chili sauce.