hi germ
more than enough time.
lint,
suan lum have more home decor stuff/ gifts etc like a mini chatuchat except more orderly and more clean.
Patpong in terms of shopping more expensive and unless u know thai, u wun get good bargains there. On the other hand, patpong is the place to go to see girlie show, bar-pole dancing etc.. or just to soak in the atmosphere of the crowd there.
if im not mistaken suan lum closes at 12am while patpong at 1am.
anyway u can spend few hrs in patpong and another few hrs in suan lum.