I think it was last year rather than "one day", both second half of last year and first half of this year were profitable. Tiger is fairly profitable overall and it certainly isn't coming from Australia so Singapore must be doing pretty well. And if Tiger can make very good profits in Singapore it doesn't seem that difficult to believe that J* Asia is profitable.
Jetstar Asia has a bleak future in its current form, not to mention that Tiger will be twice the size of them by the years end which is where the problems begin. They are playing in a market with two carriers (AirAsia/Tiger) that have the two lowest cost bases for any LCC in the industry. AirAsia has a CASK of $3.58, Tiger $3.65 and Jetstar Asia sits at $6.8. J* spent something like 100m a year on marketing to "rejuvenate" their brand up there, whilst Tiger spends 1.5m a year on marketing and is Singapore's most visited website in the airline carrier category, paying these celebrity star jumpers just dosn't cut it. They have no choice to match their competitors airfares, they might make money of them but J* Asia sure doesn't.
Foreign exchange is not in there favour either with a 25% loss from SGD to AUD.