Gregory Lacy - When the Expiry Date of First Year of your O-A Multi Entry Visa is approaching - a day or two BEFORE that Expiry Date - do a Border Run - Exit and Reenter Thailand on the same day (no reentry permit wanted or needed).
Upon reentering Thailand just before the First Year Expiry Date you will be Stamped In for 12 more months. After that if you leave Thailand you need to buy a Reentry Permit..
You don't need to get any Extension from Thai Immigration unil towards the End of the Second Year.
If others say anything different - they are Wrong!
If you are in the First Year of your O-A Visa then no Reentry Permit is needed (because it is a Multi-Entry Visa). If you are in the Second Year of Permission to Stay in Thailand you must buy a Reentry Permit
The 'settlement is called PR - Permanent Resident Status. The truth of the matter is that only a few are given out each year. Even if vigilant about gaining and sticking to the path of requirements... There is no guarantee you will ever get it.
You apply for the O-A visa in Australia using Aussi Dollars in Aussie Bank equivalent to 800,000 Baht - plus a medical check and Police background check.
My point is - the Elephant in the room that no one wants to talk about - is that some of these companies can't or won't provide these documents. Thus if the employee wants to work for that company - the employee will have to get a new non Imm B 90 day Visa - every 3 months
An Extension of Stay of a 90 day B Visa (done at Thai Immigration) requires extensive documentation about the Employee and about the Employer. For a Foreign Employee - the Employer submits company Certification, Tax and Share Documents, Employee Social Fund Payment Receipts (up to the last 3 months, Income Tax payments done for the Foreign Employee for prior months / year, Revenue Dept. Tax Id obtained for the Foreign Employee, plus misc. Docs