It is best to let it thaw naturally. Just leave the fish in the fridge a few hours before cooking, and you are done. The cool temperature will slowly melt the ice while ensuring an adequate coolness to prevent the growth of bacteria.
A common mistake in the kitchen is to thaw frozen food at room temperature. When frozen food (especially fish and meat) is exposed to room temperatures, it is more likely to go rancid. As a consequence, bacteria can multiply at a faster pace.
In this fashion, never should we thaw frozen fish in warm water. The sudden change in temperature will make the fish mushy. Moreover, high temperatures and humidity are perfect environments for bacteria to grow.
Plus, defrosting food takes time. Patience is the key here. Ideally, you can leave your desired piece of smoked salmon to thaw in the fridge overnight and cook it the next day.
After completing the defrosting phase, you can take the fish out of the fridge and make your favorite salmon recipes. Thawed smoked salmon should be cooked as soon as possible as there is nothing left to maintain its freshness. According to Still Tasty, the estimated time for refrigerator thawing is 24 hours for every 5 pounds of meat. Calculate a reasonable time for cooking fish right after defrosting.
Also, once the fish is already defrosted, you shouldn't return it to the freezer. When meat, fish, etc. are placed in cold environments, most bacteria, molds, and yeast temporarily stop growing. Think of this as hibernating. And when the fish is thawed, at the right temperature, they revive, continuing to multiply. So, repeating freezing smoked salmon will promote the growth of bacteria, which can become a health hazard in certain cases.