I am 99% certain that this is the place I was just at 20 minutes ago. It is in Villa Market, under a sign reading "Wash Me". T-shirt washing costs 55 baht per piece, and they didn't have any prices posted for socks or underwear. I ought have asked for rates or whether they launder unmentionables but hate asking for help. I think that this area is too well-to-do to have many cheap laundry places. I haven't noticed any other drop-off places. If anyone knows of other options near the Chit Lom station, I would be hugely grateful, as I'll be around here for a while. Villa Market is pretty good on other fronts, though. The wine selection is good and fairly priced for Thailand, and I was able to find gluten-free crackers that larger supermarkets did not have.