Well, aren't soft spots better than cracks ?

Oh, sorry, I forgot, inappropriate

With large areas of Bangkok considered as swamp land, is there anywhere they could have built the airport and still be centrally located and not be on swamp land? I didn't read swamp land as being an issue, it's the use of sub standard bitumen and other lower quality materials isn't it?

Personally I think it's a great airport and impressive to look at.
Only things from a personal pov I don't like are lack of seating in the check in area.
A few more immigration/customs points would be good on arrival to help clear the hundreds of inbound people but in saying that the Thai national entry point is easy with my wife and hardly any lineup at all. Other than that I think it's a great airport. I even love one of the Chinese style restaurants there who do a melt of the bone braised pork rib dish-delicious!

So the overcrowding issue Thailand should be boasting about. It's a hugely popular destination they should be proud of.

Building in a swampy area is no real problem. It just requires some more preparations and continuous maintenance. A matter of planning as it were.

Amsterdam Airport Schiphol is build on the bottom of a former lake (pumped dry between 1848 and 1852, using the Watt-design reciprocal stroke steam engine). Runways are at 3m below sea level. Infrastructure is needed to keep things dry. Roads need to be resurfaced every few years because of irregular and ongoing settling. Same with runways. A known issue, a planned maintenance.

Now back to Thailand, the hub of other things.

Terminal facilities at the regionals are the problem for this.  CNX for example terminal wise has trouble handling the incomming international it has and these are almost exclusively narrow body aircraft.