Beat the eggs. Whisk the eggs in a bowl until the yolks and whites are fully combined but not frothy. Stir in the fish sauce, sugar, pepper, and scallions.

Heat the pan. Set a 9-inch skillet over medium-high heat, add the oil, and swirl to coat. The oil should shimmer — hot enough that the egg sizzles on contact, not so hot that it browns instantly.

Pour and settle. Pour in the egg mixture and tilt the pan so it spreads evenly. Let it sit undisturbed for about 30 seconds so the bottom sets.

Cook through. Reduce the heat to medium. Cook 3 minutes, lifting the edges occasionally and tilting the pan so uncooked egg runs underneath. The omelet must be fully set — no wet or runny spots on top — before it comes out of the pan. If the top is still wet while the bottom is browning, lower the heat and cover the pan for 1 minute.

Flip or fold. Either flip the whole omelet (a plate over the pan works) and cook 1 minute more, or fold it in half and let the residual heat finish the center. Cut into wedges and serve hot over rice.