Two separate tickets from Singapore, but one w/ layover

I'm visiting Chengdu for 72 hours in 2 weeks. As a US Citizen (PR in Singapore), visas are almost prohibitively expensive. Here's my itinerary as it stands:

Flight in: Singapore -> Kuala Lumpur (3 hour layover) -> Chengdu (SAME TICKET) though presumably separate boarding passes
Flight out: Chengdu -> Singapore (direct)

If I leave Kuala Lumpur Airport and get a stamp, would that count as me coming in from a 3rd country, therefore qualifying for a 72 hour transit visa? Or should I just shell out the money and be safe?