The same airport that I got pulled aside and questioned coming in on a tourist visa after just one border bounce and extension previously.
There is little rhyme or reason to why some people sail through again and again, and others get questioned after their 2nd-3rd entry/third month here.
Some people, like yourself, get very lucky. But in general, the more time you're here on tourist visas & waivers, the higher the likelihood gets that they'll pull you back to the office and question you.
In theory, you can both get and use back-to-back tourist visas for years on end. There is no official limit, although many consulates have a one-and-done policy.
However, having a visa doesn't guarantee entry, and it will eventually get to the point where immigration officers will summon you to the back room and question whether you are a genuine tourist, having been here 6, 9, or more months on consecutive tourist visas.
It'll be up to the immigration officer you're in front of, but if you try to come in on another tourist visa or visa exemption straight after (or not very long after) spending 9 months of the year here on a maxed-out tourist visa, you have a *high* likelihood of being pulled aside and asked what you're doing here, and whether you are actually a tourist.
We always get some people posting claiming to have found the kind of holy grail, the formula etc which imm officers use to determine if someone can come in or not.
Some even claim to have found *the* way to *always* get in every time. The proverbial keyboard shortcuts.
The reality is, after 1 or two entries, it basically is just dumb luck. There's no pattern or reason to why some people get questioned after their third or even second entry, while others get away with it for more than a year, ir even two years.
There are some individuals who are in a special state of denial there's any kind of tightening and that its totally stress-free to just stay here indefinitely on Tourist visas & exemptions.
I've been here since 2013, just before the coup. When I got here, people were just living here for decades on serial border runs, Thai wives, illegal work in a small town school etc.
Then the crackdown happened circa Feb-March 2014. Everyone said it wouldn't last, everyone said that it would totally go back to the old days soon.
Welp, turns out they were in fact serious, and the rules simply got codified, or at least made less chaotic, leading us to the current situation where imm officers are given all the discretion, but with guidelines that anyone suspected of using the tourist visa system to just live here should be questioned.
Perhaps you mean, can I keep coming in and out on tourist visas (which with the extension each get you a 90 day stay)?
If so, then I'm afraid thats no longer the easy way to stay here it once was.
First of all, more and more (probably most, at this point) Thai consulates will no longer issue you a second tourist visa if you've just had one.
Secondly, immigration officers at the airports and land border checkpoints are becoming more strict about people using short-term tourist stays as a means to basically live here.
These days, at some point after being here anywhere between 6-12 months (maybe longer or shorter depending on which immigration officer you end up in front of), on your way back in, immigration officers are likely to pull you aside and question you on what you're doing here for such a long time on tourist visas. At some point, you risk being denied entry.