I flew with CI from TPE to BKK in J last month with a 16 hour overnight layover. Your bags will not be checked through on the overnight layover, unfortunately. You will need to pick them up in TPE. However there are lockers you can leave them in if you prefer not to haul them into the city.
The lounge is decent (poor drinks selection) but what really irked me was the lack of fast track security even for J pax. I had to wait almost one hour to get through security. This was at 5:30am.
Perhaps the lines are shorter at other times?