"Oh yeah, my single went to Number One yesterday." I don't think he is trying to be cool, nor is he cross I did not know Stay With Me (not the Faces song) had topped the charts in its first week of release, although I clearly should have. My ignorance extended to a lack of awareness he had performed at Radio 1's Big Weekend, although I should have known that too. "It's okay, I was on the Other Stage," he says.
Now his debut album has continued the run of success by entering the chart in the top slot, and I have learned to pay attention.
In my defence, a lot is happening in the life of this young man, who also had a birthday (his 22nd) during the period over which our chat has been arranged and postponed more than once.
So if I was not quite up to speed with his career, it is because it is moving quite fast. Speaking while he was in Glasgow was never on the schedule, so he had been greeting fans in Manchester when we eventually link up.
He enjoyed the performances by Rita Ora and London Grammar at Glasgow Green he tells me, and being top of the hit parade is never mentioned again. Sam Smith is not one to brag, but he does have a story he wants to tell about his debut album, and if it sounds a little well-rehearsed, well, he has probably had to tell it a few times recently.
The set's narrative is a Tears Of A Clown/Only The Lonely tale, and just as it served Smokey and Sinatra, it will suit Smith very well. As well as the classy threads he often sports in fact. I ask if a soul record was what he set out to make, because that is how it sounds to me, and at last I may have said the right thing.
"I listened to soul music from a very young age (his mother's influence, one understands), and my voice is a soul voice, so even if a song starts out country or gospel, my voice turns it into that."
It is also that voice that brings a consistency to an album on which he has collaborated with a number of more experienced writers.
"Every song is the result of a writing session with someone else, but I have chosen the ones that are most personal, because I wanted a story on the album. It is about unrequited love and the romantic side of the one-night stand."
Which is Smith's way of saying there is no-one special in his life, and never has been, beyond a crush the other party was likely never aware of.
"I can't contribute any advice about relationships, because that person did not love me back. So I wanted to put loneliness on a pedestal more than it is."
It is clear that Smith - or someone else - has put a bit of thought into this tale, because his career so far has been much less structured. He came to the attention of the world through lending his voice to dance tracks by Disclosure and Naughty Boy, both of them huge international hits, and a gift to a young man trying to make his way in the music business.
"I was working in a bar when I met producer James Napier (aka Jimmy Napes), and I was willing to sing anything." He still is, he tells me, determined the more mellow music that graces his own album is not the full extent of his career. But further studio-based work will not be at the expense of his new solo persona, and fronting a real band of live players.
"We are getting better and better by the day and I want to put on a show with real instruments and real singing. It's a hugely different experience."
The contemporaries he admires, he says, are those who do just that, and can cut it on the live stage, namechecking Adele, Emeli Sande, Paolo Nutini and Ed Sheeran.
"That is what is needed in mainstream music," says young Mr Smith, "less gloss and more grit."
Sam Smith's In The Lonely Hour is out now on Capitol.