"Say hey kid" is a common phrase used to greet someone in a casual or friendly way. If you're looking for synonyms to replace this phrase, there are many options you can consider. Some possible alternatives include "hello there," "hey there," "hiya," "yo," "what's up," "hey dude," "hey man," "sup," "hi," or "howdy." Each of these phrases can be used to convey a similar sense of greeting and friendliness, and can be customized to fit your personal style or the situation at hand. Experiment with different options to find the right one for you and your intended audience.