If you say "Tú no me tocas" you mean "You don't touch me". You're basically referring to a factual situation.
If what you want is to use an imperative, you need to say "Tú, no me toques" or "No me toques".
In some contexts, "Tú no me tocas" can be used with that purpose but it's not very common. I would recommend you use the forms I suggested, that seem more natural in most Spanish speaking countries.