That's it exactly. If we are required by law to get tax numbers and do tax returns and pay some tax because we are tax RESIDENTS, then we are no longer tourists, visitors or guests, we are residents. Therefore we should be issued with resident ID cards that distinguish us from tourists, so we get the Thai price at national parks and hospitals and all the other things that have dual pricing.
This is what I've always assumed to be the ultimate reason that the EU requires tourists to not stay in the territory for more than 90 out of any given 180 day stretch; they might have to include us in resident systems if they allowed it longer officially. A quick Google search, however, does not confirm my assumption. If anyone has better info, please chime in, and it probably applies to LOS in some way also. FWIW, I'm an American in Italy now (home is Bangkok) counting my days.