The first lines of "Non sum qualis eram bonae sub regno Cynarae" plunge readers into a luxuriant world of wine, kisses, and hauntings. Right from the start, the poem's tone is both sensuous and sad.
The speaker begins with a direct apostrophe:
Last night, ah, yesternight, betwixt her lips and mine
There fell thy shadow, Cynara! [...]
This Cynara seems to be a lost lover—and one the speaker can't forget, even as he relishes the "kisses and the wine" of what otherwise sounds like a pretty enjoyable evening. Whether she's dead or simply absent, Cynara is a "shadow" that remains out of his reach. But his apostrophe to her suggests that she's also always with him—at least in some way.
The speaker's use of archaic words like "yesternight" and "betwixt"—along with his image of Cynara's "breath" falling on his very "soul"—makes him seem like a romantic fellow. So does the rhythm of his verse. Take a look at the way he uses caesura in these first three lines:
Last night, || ah, || yesternight, || betwixt her lips and mine
There fell thy shadow, || Cynara! || thy breath was shed
Upon my soul between the kisses and the wine;
These mid-line pauses slow the poem's rhythm down before it's even had a chance to get into gear, inviting readers to linger over these words. The "ah" emphasizes this effect, since it sounds drawn out like a long sigh between commas.
This stanza also starts a pattern of caesura that will continue throughout the poem: the speaker never once says Cynara's name without following it up with a dramatic exclamation point. The thought of her, it seems, stops him sharply in his tracks.
Although these opening lines (and the entire poem, for that matter) don't provide any identifying information about the speaker, it's clear that the speaker bears a strong resemblance to the poem's author, Ernest Dowson. Dowson was a member of the melancholy but pleasure-loving Decadent movement, and often wrote about (and suffered from) tragic love. Since it's clear that this poem will explore those themes, it seems fair to conflate the speaker with Dowson himself.