I am looking to replace some spray paint off plastic surface, the plastic is pretty soft I don't want to damage it.
It depends on both the plastic and the paint. Most spray paints cannot be easily removed from plastic, but if it's the right kind of plastic, you can put nearly any solvent on it. The best approach is to start with the less aggressive ones, like mineral spirits and goo-gone, and apply a little solvent to a spot that doesn't show. Let it sit there in a drop for a few seconds and wipe it off. If it leaves a hazy or sticky spot, then that solvent will definitely dissolve the plastic. If it wipes cleanly off, it's probably safe to try. If you have no luck you can move on to methyl ethyl ketone (MEK), acetone, and even gasoline, but these are the ones that melt most plastics. If it's a copolymer or resin, then you might be okay with just about any kind of solvent.
