Place it right after the fake-innocent moment peaks, then follow it with the Kiko Laugh Sound Effect to release the tension, and use the WhatsApp Message Sound just before it to frame the exchange as a chat reply.
About this sound
A Portuguese voice clip delivers the saying 'o esperto se faz de bobo' in a knowing, slightly sarcastic tone, as if the speaker has already worked out the situation and is choosing to act naive. It feels sly, amused and quietly mocking, turning a pretend misunderstanding into a sharp little callout.