|Clean the fish, keeping head, tail and fins attached. Rinse and drain well. Cut two diagonal gashes to bone level on each side of the fish. Sprinkle a thin coating of salt and rub evenly over fish, including the body cavity and the gashes. Set aside.|
|Heat a wok till hot. Swirl in the oil to coat its surface. When oil is hot, gently slide the fish into the wok and fry 1-2 minutes on each side, enough to lightly brown.|
|Transfer to a shallow dish which fits in the steamer rack of your steamer. Arrange the garlic, chillies and ginger on the fish. Sprinkle over the top some light soy sauce or fish sauce, sugar and 1-2 tablespoons of the oil left in the wok.|
|Bring 1 1/2 inches of water to a boil in the steamer pot before placing the rack with the fish over it. Cover and steam over medium-high heat for about 8 minutes.|
|Open the lid and sprinkle the green onion pieces over the fish. Cover and steam another minute.|
|Remove from steamer, squeeze lime juice over the top and serve while still hot.|
source: Thai Food & Travel
You can also make this without pre-frying the fish in the wok. It will be somewhat less tasty, however.