Bear in mind that if Country A has its suspicions, they can easily enough thumb through your passport when you enter, notice the lack of recent stamps indicating entry or exit elsewhere and ask where -- and how -- you've been spending your time since you last left Country A on that passport. Ditto on departure. "And your final destination is?" Again, only if they want to be suspicious. And it's well known that officials of some Country A's in Asia are suspicious, precisely because the dual passport problem has become so widespread there.