Thailand Is Just Another Life-Consuming Recreational Drug
Some chain-smoke, some smoke only socially, and some don't smoke or have never smoked.
Some are alcoholics, some drink only socially, and some don't drink or have never drunk.
Some are addicted to gambling, and you can guess the rest.
Yes, most people have vices, and from my point of view, Thailand is simply another in a long list of "recreational drugs" that get under certain susceptible people's skin and begin to consume part or all of their life / time / money / thoughts. Be it spending as much vacation time as possible there each year, year after year, or walking away from life in the west to start over in Thailand, and although the vast majority of westerners go through their life never feeling any urge to emigrate to a poor, hot, corrupt South-East Asian country, the place does appear to have a drug-like hold over many westerners. This seems similar to how a drug such as cocaine might take a hold of somebody, but instead of chemically, Thailand does it purely psychologically, praying on those who feel that much is lacking in their life and who feel a strong desire to change that, but via geography rather than other means. Cocaine users didn't miss the buzz of using their substance of choice until they had experienced it and realised that being stoned feels better than not being stoned. Some then do it occasionally, and some 24/7.
As with cocaine, Thailand allows the "user" to feel completely different, detached from their normal existence, as if they've entered a whole new universe and state of mind & being. The mundaneness of their usual existence has all but gone, and many of them never want to return to that, doing everything they can to find a way to permanently fund this new sensation. The term "novelty farang" also stems from this, whereby those affected get a huge buzz out of being different and being noticed by Thais. Is it similar to the drive that makes certain people crave fame and stardom? Perhaps. They also find like-minded westerners who are doing the same thing, and form new friendships accordingly (much like alcoholics in a pub, smokers stood outside the pub, or junkies in an opium den feed off each other's addiction).
The "lord it over the locals" effect is also a strong draw, whereby those who would be "nobodies" back in their homeland suddenly find themselves in a place where they are often the most educated and wealthy person within view, which causes an artificial ego-boost, or whereby labour is cheap and so those who have never been able to afford pampering before (taxis, maids, laundry, restaurants) find themselves able to achieve something they have always craved but never had. Dare I say it, but it allows losers to become winners, merely by going somewhere where the locals are mostly even greater losers (in worldwide economic stakes).
Upon finding this lifestyle niche, their personalised combination of "novelty farang" syndrome, "lord it over the locals" syndrome, and "birds of a feather" syndrome, many exert huge amounts of effort to hang onto it.
Strangely, those addicted to Thailand seem to much more aggressively defend, justify, or refute any suggestion about their addiction, as if theirs is a normal, healthy addiction, or not an addiction at all, simply a "life choice" that they are fortunate or clever enough to have discovered and grasped with both hands. To them I say that they (or their ego) are deceiving themselves, because they would no more enjoy the thought of having to be permanently back in their birthland than an alcoholic likes the thought that his last ever drink has already passed his lips. If they were to be sent back to their homeland, many would suffer "cold turkey" symptoms in a similar manner to an alcoholic on the wagon or a junkie on rehab against his or her will.
It is this strong hold that causes westerners, especially those in their 20s and 30s (many many of whom can be spotted trying to earn a living on the streets of Bangkok) who would otherwise be back in their homelands building a life / career / family, to throw caution to the wind and start their life over, with an alternative life / career / family. In the same way that a junkie who might otherwise have become a lawyer or supermarket manager instead makes a living via selling drugs or burglarising houses, these types often instead resort to selling the English language or working as bar managers (pimps?), with less than admirable images attached to both of these roles.
Some love drinking heavily and never want to stop. Some love chain-smoking and only wish they could do it fulltime. Some love gambling and only wish they had unlimited funds to pursue their passion. Some love heroin or cocaine and wish that they were more freely available. And some are hopelessly addicted to Thailand (although in their euphoric state, few, including yourself perhaps, seem to be aware of it). The fact that it is a place and not some more commonly categorised addiction does not in my opinion mean that it is not an addiction, but merely that this type of life-changing addiction has yet to be formally studied and documented, as there has been no need or desire to do so.
There sure are many who suffer from the affliction you describe, and would do anything they could to remain in Thailand if they were told that they had to leave.