Back then (>5 years ago) I regularly parked overnight there to take flights. Longest is CNY IIRC, one whole week.

It used to be just RM3 or 4 per day. KLIA transit from TBS to KLIA/LCCT also very cheap back then.

My friend tried the park and ride car park next to LRT station just last year, and he said it’s fine too for overnight.