Put the noodles in a large bowl and cover with hot tap water; let soak while you prepare the other ingredients.
In a 3-quart saucepan, bring the broth, garlic, ginger, and soy sauce to a rapid simmer over medium-high heat. Cover and continue to simmer for 10 minutes; remove and discard the garlic and ginger.
Add the glass noodles to the broth and cook until nearly transparent (you should see only a tiny thread of white in the center of each noodle), about 4 minutes. Using tongs, distribute the noodles among 4 bowls.
Add the bok choy to the broth and cook, uncovered, just until the white parts start to become tender, 3 to 4 minutes. Using a hand-held strainer or slotted spoon, remove the bok choy and distribute among the bowls.
Add the turkey to the broth and simmer just until heated through, about 30 seconds. Distribute the turkey and broth among the bowls. Top with the scallions and serve with more soy sauce on the side.