Its already happening. I had a young dude complain to me that Siem is starting to look like an old age home.
If you dont have a Thai wife, and if you are too old for round the clock fleshpots, and you need a change of scene, and you like the old timier Asian city vibe, and you dont want to hassle with all the BS the Thai govt lays on you, you just come on over be 55, pay their $300 and come and go as you please. Horny? $27 bus to Bangkok.
You can even get to Buriram and Surin quickly for a change of scene.
Ive met 5 guys here (Americans) who ditched their retirement Visas in Thailand because of tax uncertainty. One of them rents a (nice) $100 studio here and has a condo in BKK. He follows the air, the seasons, the hormones. Hes younger than me though. I wish this place would have been livable 15 years ago.