I fear you could be right about KTA. To my mind it is absurdly far out of the centre of BKK.
There is a standard-gauge, high speed line to Laos under construction, but not finished. If that gets completed then there will be a competitive route to Udon Thani and beyond.
The main metre-gauge routes (southern, northern and north eastern) seem to be having their single tracks upgraded to double track so that more trains can be run (but are there modern trains on the way?). I understand that within 5 years for example the north-eastern line to Ubon Ratchathani is intended to have more and faster trains. I think there's also an east - west railway under construction; but there seem to be so many projects on the go at once.
For our part, my girlfriend and I like to use the sleeper trains to go north or south overnight. They're usually comfortable, and the price is reasonable compared with a hotel - you don't get breakfast but you do get to wake up hundreds of kilometres away from where you started!
You'll need to file a new TM30 before the online TM47 will work for you.
I had the same experience and discovered the system had picked up on my one year old BKK visit and hotel stay. Weird thing was I'd stayed in 4 other Th hotels since and never changed my home address. I simply did a local drive thru 90 day, easy as, and will file a new TM30, when time permits, to get the online system back into sync.
I'll also make a point of only using DL or pink card for hotel check in as old ID data fails to register and hotels don't seem to follow up.