One thing you do have to remember is that in Thailand there is no one rule fits all. Example, the requirements for extensions are specific to each immigration office. So you can ask a question and get different answers which are all correct but specific to an individual office. The flippant remarks posted by some with nothing better to do aren't difficult to filter out.
The 800k has to remain in your account for 3 months after the extension is granted and be back in 2 months before you apply for your next extension. Can never go below 400k for remaining 7 months.
I'm not 65 until January and I've spoken to International Services on at least two occasions and they've been extremely helpful, I guess it just depends on who you get. But they are right, you can't apply until you have your pension. There will be an application form to complete, they'll require proof that your moving (tickets, address etc), they'll also require which bank you want the pension paid into (you can elect a NZ one or Thai one). You will also be required to have an interview which they told me can be arranged by phone in many cases. Hope this helps and clarifies how it works.
First thing go to the MSD website and navigate to the section on pensions and living overseas, most of your questions will be answered there. Basically there are 3 categories; countries NZ has SSAs with, Pacific island countries, other countries (which includes Thailand). For other countries how much you will receive depends on how long you lived in NZ between the age of 20 and 65. If you lived here the entire time you will get the full amount. If not you get
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th for each month lived in NZ between those ages (45 years = 540 months).