Combine chicken, 1 tablespoon water, 1 teaspoon cornstarch, soy sauce, and baking soda in bowl. Let stand at room temperature while preparing other ingredients.

In liquid measuring cup, beat eggs and 2 teaspoons water with fork until whites and yolks are thoroughly combined and color is pure yellow; set aside.

Mix ½ cup chicken broth and remaining 3 tablespoons cornstarch in small bowl until thoroughly combined; set aside.

Process 2½ cups corn and remaining ½ cup water in blender on low speed until thick puree forms, about 30 seconds.

Increase speed to high and continue to process until smooth, about 1 minute longer.

Strain puree through fine-mesh strainer set over large saucepan. Using back of ladle or rubber spatula, push puree through strainer, extracting as much liquid as possible. Discard solids.

Add ham, salt, white pepper, remaining 3½ cups broth, and remaining 2½ cups corn to corn puree.

Bring to boil over medium-high heat. Reduce heat to maintain simmer and add chicken, stirring to break up any clumps.

Partially cover and simmer for 5 minutes (broth may look curdled as it comes to simmer).

Stir broth-cornstarch mixture to recombine. Add to soup and cook, uncovered, stirring occasionally, until soup has thickened slightly, about 2 minutes.

Holding fork in your hand and measuring cup with egg mixture in your other hand, slowly pour egg mixture in slow, steady stream through tines of fork in concentric circles over saucepan until ribbons of coagulated egg form, about 1 minute.

Season soup with salt and white pepper to taste.

Gently ladle soup into bowls, sprinkle with scallion, and serve.