I don't see any way to tell samba for OS/2 how to do that.
The user ID and password, is in the Output Port driver (SMB.PDR) settings. I think it defaults to GUEST, but it can be set.
I just tried it (with SMB.PDR dated 5 Dec 2012, from eCS 2.2 beta - bldlevel says it is 1.02.02). I see the print job in the local printer, then I see it in the remote printer, the printer wakes up, and the job goes away, as if it had finished, but nothing prints. Doing the same thing on the printer host system, I see the job go to the local printer, the printer wakes up, and the page prints.
Doug, that version of SMB.PDR is very old and lacks some important fixes.
The latest version is 1.03 and is included in the most recent test ISOs of eCS 2.2.
Hmmm. Now I remember that there was a problem there. That needs to be fixed.
I haven't tried to use the SAMBA printing support recently (about a year). I have been trying to get CUPS to work over the network (with not much success - it seems to block access, because there is no user ID and password - I can find no place to insert that information). It is not a priority, for me, anyway, since I rarely print anything, except test prints, any more.
FWIW, the whole SAMBA Wiki is a real mess. It is very difficult to figure out what the latest, recommended, versions are, and some of the later ones don't work very well.
As noted above, 1.02.02 seems to be the newest that I can find, although I do remember something about version 1.03.