@Tin *********
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.