144 hr transit

Yes, this route would be eligible for 144 hours visa free transit.

Anyway, I find one difficulty and this is the fact that currently there are no flights between Chengdu and Kuala Lumpur.

So, you should be aware that you cannot book a flight that would look like:

Singapore - Chengdu - Singapore - Kuala Lumpur

Only the immediate points before and after the Chinese destination are relevant.