1Finely shred the peel from the lime, then juice the lime. Set aside the lime peel.
2In a large saucepan over medium heat, combine the lime juice, coconut milk, thai chili, and sugar.
3Cut fish into 8 portions; rinse and pat dry with paper towels. Rub salt on fish portions, then place fish pieces in coconut milk mixture in saucepan. Cook fish, covered, for 5 minutes. Uncover; gently stir in bok choy, and cook 3 to 5 minutes or until fish flakes easily when tested with a fork.
4Ladle fish with cooking liquid into individual serving bowls. Top with lime peel and, if desired, ginger and green chili garnish.