Yes that's true, but it's not that simple. As I've explained in my response to your other post, DTAs play a huge part in whether expats are actually tax resident in Thailand. There are way too many variables to be able to categorically state someone is "liable" for taxation in Thailand.
Being positive whilst ignoring the obvious means a person is living in a delusional world. I guess in your world there's no poverty either. It's great that you've reached your little Nirvana
Only money transferred into Thailand is possibly taxable, although you're correct, a lot depends on the respective DTA. I can see a lot of retirees now bringing in cash each time they travel. This stays under the radar as far as the tax office is concerned
Never once did I say you can apply in Thailand, although many do and then simply bounce to activate it, but there are a number of easily accessible neighbouring countries in order to do this. It's very easy to set up a business name and give yourself a contract, that's how a few I know who have done it. There's no proof of income required, just a simple 500k in a bank or super fund in your home country. For regular travellers like myself the benefits are very good. Less cost over five years and the absolute best is no need to ever visit an immigration office in Thailand and put up with their pedantic inconsistencies! There's no financial criteria within Thailand, so very easy to stay way under the taxation radar. It's to each their own. For those happy to sit in Thailand year in year out the non-O is best, but for avid world travellers the DTV is the best retirement visa!