SQ generally will interline to any airline under their IATA agreement but i have not experienced it with non- * alliance carriers and normally most airlines tend to be reluctant to interline if flights are beyond a "24 hour period/same day period."

Nonetheless, the airport referenced being changi airport is perhaps one of the most efficient in the world and pax who are not on budget carriers, ie airlines that depart from T1, T2 and T3 generally are able to simply to sort out the check-in formalities without having to pass immigration. Ie, when u go to the transfer counter, simply hand over the baggage tags and the changi folks will do " their magic" behind the scenes. No need to collect baggage.

Just don't do stupid things like bringing in drugs.