You can aerial the approach. Dair is great for stuffing dash attack, and bair and nair can also work well. If he isn't ASDIing down (until later percents) and grabbing out of hit, ftilt can work decently here too. Dashattack tends to be pretty punishable OoS if you don't lightshield and shield DI in. A well timed spotdodge can also work (it's decent vs Marth's pretty much everything because of his lack of active frames, but he might just dash dance grab you when you start doing this, and a nair at the timing of most other moves he could throw out will probably hit you).
Try not to laser at range for him to do these or too much. Try to change positioning while lasering.
