1. Thaw cherries, reserving juice (about 2 Tbsp.). Sprinkle gelatin over 1 cup coconut milk in a medium bowl. Let stand.
2. Meanwhile, bring sugar, next 2 ingredients, cardamom (if desired), and remaining 3 cups coconut milk to a simmer in a saucepan over medium-low heat, whisking constantly.
3. Pour hot coconut mixture over gelatin mixture. Stir until gelatin dissolves. Stir in reserved cherry juice. Let stand 20 minutes.
4. Lightly grease a 6-cup gelatin mold with cooking spray; place cherries in a single layer in bottom of mold. Pour enough gelatin mixture over cherries to cover halfway. Chill 20 to 30 minutes or until slightly set. (Let remaining gelatin mixture stand at room temperature.)
5. Slowly pour enough remaining gelatin mixture into mold just to cover cherries. Chill 20 to 30 minutes or until slightly set.
6. Slowly pour remaining gelatin mixture into mold, and chill 6 hours or until firm.
7. Gently run a small knife around outer edge of mold to break seal. Dip bottom of mold in warm water for about 10 seconds. Unmold onto a serving plate.
*Fresh pitted cherries may be substituted. Omit cherry juice in Step 3.
Note: We tested with Thai Kitchen Coconut Milk.