If I was taking family/wife etc then would spend the extra to make it a conducive time for all. If it was just me, and I suppose some of the big post I made earlier, was assuming I was on my own and time was restricted, then I would get into a different "mode" and adventure and "rough it" to enjoy the wonders of not having anything to worry about and feel like I did when I first got here. Don't get many chances to do that properly now.
The train, sleeper/1st class, would be the most acceptable/cost effective/harassment free option if you were traveling on your lonesome. If I had the Mrs or kids with me then I would probably drive or rent a car, staying at a few places along the way and make it an enjoyable family trip.
If on my own then I would just "rough it", get it done, get pissed along the way, enjoy myself within parameters, get back home to where I belong.

It's a pitty you can't fly from HH to Udon Thani, that would be the answer.

Many thanks DM, but not in HH till next month, will PM you when. Chok dii
