Commute?!?
For starters on a Scoot roster there's hardly enough consecutive days off to make it worth living off the island when you're not on duty, but if you're brave then consider this...
You willl hold a Singaporean work permit which will smooth the way through Singaporean Immigration (presumably without the usual Entry Card or date stamps), but if you're not Malaysian then entry into Malaysia, whether it be Johor or KL, will be as a tourist (Social Visit Pass of xx days). Fortunately Malaysia has done away with the Entry Card (don't know why Singapore persists with it), but the entry stamp and corresponding exit stamp will take up one half of a passport page each time - 8 times in a month, that's 4 pages of a typical 32 page passport... do you like filing for new passports all the time?
Then there's the Causeway, anyone who's crossed during rush hour (which seems to be most of the time except the wee small hours) would know it's probably faster to swim. Tuas link works better, but it's a longer drive and more toll. Fly to KUL or SZB, can, but when you take the time required and cost of the fares you're just buying yourself a headache.
Malaysians in SQ have commuted in the past - it only really works for them, not for anyone else.