Been in this situation quite a lot of times at different work places and I suggest you to be clear about your intentions with him. You really don’t want things to go nasty at work so try to be considerate while you’re at it.

There tends to be a lot of helping each other out with costumer service jobs so others might think you go out of your way to help them but maybe you just want a good work flow. I’d do simple gestures like saying “thanks man/bro” or say it’ll be more enjoyable having other staff/friends when you guys go out. If you guys talk often, try mentioning another guy maybe they’ll get it? Set boundaries but be respectful of their feeling/interest in you too to avoid work drama.