Good pointer by
bpk6h as to the zones in J on A388 upper deck (also applies to the lower deck Eco cabin). Actually, IIRC there was a time several years ago when SQ flights used to be quite cold in general and a lot of people asked for blankets and such. I know folks who always would wear long sleeve onboard and bring a cardigan or so.
These days that is not necessarily the case any longer and definitely overall cabin temperature seems to have been increased by a few degrees. Could have been a move due to passenger feedback and also helps with fuel consumption and all that I guess.