I am flying MEL>SIN on SQ and then SIN>KBV on TG (return) in Oct, and Tiger have informed me (I rang them to check) that I'll need to enter Singapore to retrieve my bags, recheck them, and go back through Singapore immigration...both ways. They don't interline baggage with anybody, and their "tigerconnect" service only does Tiger<>Tiger connections! (
You have to pay extra for that!!?? 
)
Fortunately this isn't too much of a hassle at super-efficient Changi but is yet another reason why I avoid flying with budget airlines! Anybody else had this experience...or a different one?