Flight out is 1030hrs. Cannot seem to find a hotel in Chitose.
Safe to leave Sapporo early morning for the flight? Coz I still have to return car
Thai Airways ? All my Hokkaido flights have been with TG
Take JR train from Sap to CTS. Buy tickets in advance once in Sapporo & reserve your seats. The JR CSOs at Sapporo Station speak good English & very helpful. Train ride is 1hr. There is more than enough time.
I would suggest return the car in Sapporo.
Honda rental (& maybe others) does not charge extra to pickup CTS & return in Sapporo.
Dont risk driving from Sap to CTS in the morning. Besides, the car rental may not be opened so early. Do note that the car rental offices are not at the airport but 10-15 mins drive away.
It happened to me before

Luckily the staff at the long term car park said I could leave the car keys with her after she helped to call the rental company staff.
Stay near Sapporo JR station - Hotel MyStays, Gracery, Century Royal, Toyoko Inn etc All are decent & not expensive.
In Chitose, I have stayed at Grand Terrace Chitose. Has free airport shuttle, free supper & coffee but there is not much nearby.