Thai Chili Oil:
Heat oil and chilies in a small saucepan over medium heat, until it reaches 300°F. Set aside to cool to room temperature.
When cooled, pour into a blender or food processor and blend until chilies are completely pulverized. Strain through a fine-mesh strainer into an airtight container. Discard solids. (This makes more oil than you need, so the extra can be refrigerated for several weeks).
Chili-Ginger Ponzu Sauce:
Mix all ingredients in a small bowl. Refrigerate until ready to use. (Can be made 5 days ahead).
Lay scallops, slightly overlapping, on a chilled plate. Dress with enough chili-ginger ponzu sauce to completely coat. Sprinkle apple, cucumber, fried shallots and shiso on top. Garnish with lemon zest.
For a quick weeknight meal, you can sub the Thai chili oil with your favorite store-bought chili oil.
You can also make the scallop crudo with sashimi grade salmon instead.