In a small bowl, combine melted butter, rum, coconut milk, and vanilla. Set aside.
In a medium-sized bowl, whisk together the flour, baking soda, and cocoa powder. Set aside.
In a large mixing bowl, beat together the brown sugar and molasses until smooth.
Add eggs to the brown sugar mixture one at a time, beating well after each addition.
Add the flour mixture and mix until just combined.
Add the butter mixture and mix until just combined.
Fold in the coconut and chocolate chips.
Fill cupcake liners 3/4 full.
Bake at 350 F for 25 minutes or until cupcakes bounce back when lightly touched.