It all comes down to where your hotel is, i came in this week and from wheels on the ground to asok was about a hour taking the airport link and a short subway
you said “it's not immigration its when you check in they need to input the flight details when your leaving or you will be denied boarding.”
This is absolutely not true, they do not check nor care about your exit flight details. They might ask to satisfy the thai immigration requirements but it doesn’t go past a casual glance on whatever medium you’re supplying to them.
I almost always come on visa and even the couple times ive come on exempt i’ve never had to show onward travel, if anything its a casual ask how long my trip or my plans are.