Depends on where you stay... From the airport to central Bangkok is just about 30 mins. From the basement of the airport get into the train. Quite easy.
You got to figure out how to get to these places from the hotel you stay. You can take a tuk-tuk, but make sure you bargain with a couple of them. There is a new MRT line which opened up recently but not sure whether fully operational yet.
Use grab taxi or uber way cheaper than tuk
