I did this exact thing last year under the same status - except no reentry permit. I crossed over to Savannakhet - passing through Thai immigration they didn't want me to leave knowing it would cancel my Non O Extension of Stay. I had my Visa Agent talk to the Thai Immigration Suppervisor at bridge on the phone. They then let me pass canceling my Non O Extension. At that moment I had no Thai Visa status.
- The Krabi Immigration office insists on a Thai language lease or you don't get the Certificate of Residence... same for most others processes there. The lack of consistency from one office to another is the problem.
90 day reports can be easy. Two-three minutes in Krabi. Longer in big cities. There is nothing to it in most areas - except a long queue sometimes.
You show up with your passport.
Check your calander. You can go 14 days before or 7 days after the exact date. Pick a convenient date when you might include other activities. No need to pay a fee to some person or outfit you don't know. Immigration does not charge a fee.