This post doesn't make a lot of sense. If you're on a 12-month extension, where does the 90-day extension come in? There's no such thing as an "exit permit" - you don't need permission to leave. Perhaps you mean a re-entry permit? You cannot allow an extension to "lapse" - you need to leave the country before the expiry date otherwise you go onto "overstay" which is not a good strategy.
If you're asking can you live in Thailand on continuous 9-month tourism visits the answer is no. You might get away with two, but whether on the second one you are denied entry at the airport, only the immigration officer on the day can answer that one.