If your nationality is eligible for visa-exempt, yes, you will be stamped in for 30 days on it and 30 days tourism extension is applicable.
I would contact LTR BOI in advance to jump in that route to make sure there wouldn't be any issue for LTR processing in your case if the current status is changed (on retirement extension -> visa-exempt).
Better check if 5. note 3 or similar thing is applicable to your case.
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