Reading through the PHB I would argue that you would have to touch the person a.k.a. touch the ki of someone before understanding and communicating with him. Every other attack or bonus manipulating someones ki in the book does need you to "touch/hit" him aswell.
PHB pg.76:
The Magic of Ki
Monks make careful study of a magical energy that most monastic traditions call ki. This energy is an element of the magic that suffuses the multiverse - specifically, the element that flows through living bodies. Monks harness this power within themselves to create magical effects and exceed their bodies' physical capabilities, and some of their special attacks can hinder the flow of ki in their opponents. Using this energy, monks channel uncanny speed and strenglh into their unarmed strikes. As they gain experience, their martial training and their mastery of ki gives them more power over their bodies and the bodies of their foes.
Monks learn that Ki is the inner energy of soneone/somethings. "Touch the Ki" (RAW PHB pg.79: tongue of the sun and the moon) would require a touch of the inner energy.
PHB pg.80:
Quivering Palm
At 17th level, you gain the ability to set up lethal vibrations in someone's body. When you hit a creature with an unarmed strike, you can spend 3 ki points to start these imperceptible vibrations.
The Monks needs to hit someone and spend his Ki to start vibrations in someone else.
