Could the suit be a metaphor for normalcy? Loyalty?
It's also possible that Neruda's ode is really what it says it is: an ode to a suit.
Either way, the speaker isn't always considering the suit and what it means to him. After he puts it on, he forgets about it.
But notice the imagery in line 64: the suit "embraces" him. The speaker seems to feel guilty about forgetting the suit after such a positive interaction.
Could the speaker really be saying that he's guilty of taking these daily items, like a suit, for granted? After all, without them, he's unable to do the things he loves, like talk to people and write poetry.
Or maybe he's not guilty at all. The reason he forgets the suit is because it is a part of him. Maybe he doesn't need to remember it, because it's always there.
because we are one being and shall be always in the wind, through the night, the streets and the struggle, one body, maybe, maybe, one day, still.
The two "are one." They're now joined completely.
These lines remind us of the situations the two have faced together in the poem; they've battled the wind, the night, the people in the streets, and violence. And, ultimately, the two will face death together, too.
It just took looking at his suit in a new light for him to realize that the two are closer than he may have ever realized.