Pre-covid I stayed at the Phoenix Hotel. It's a 10 min drive from the airport and has free shuttles to trains as well as the airport. It's pretty basic but definitely did the job.
As a bonus it's an easy walk to a genuine (as far as I can tell) Thai restaurant (beware the chilli levels!) which I now visit every stopover in BKK. Here's the restaurant google maps link :
https://www.google.com/maps/place/%E...oASAFQAw%3D%3D