Keep it simple. You don't even know the guy anymore. He's got a wife (perhaps more than one), probably kids. Forget the past in terms of the glitzy giving of gifts ... give him money.
10,000 baht for old times sake and no future in sight. He'll love it, and you'll get to smile.
As for the stay over? Forget that, get real, way too obvious ... give him 200+ baht for a taxi home (on top of 200+ baht for a taxi to your hotel). Dinner, drinks, laughs bye bye.
Does he speak much English? Enough for an evening with Just You?