OK my last border run is in November, the usual 5 days before the visa utilisation runs out. I'm watching the exchange rate like an hawk, and my pension goes up in November. If I get over the 40K/month income before that last 90 days is up. Can I apply for the extension, or do I need to go down to Penang in January?

You can apply for the extension during the last 30 days of any permision to stay, so yes.

Your income if exchange rate is needed must be from outside Thailand would would require Embassy letter and what they will allow to be indicated and if it exceeds the required 40k at current exchange rate.

You can apply for the extension during the last 30 days of any permision to stay, so yes.

Thanks Mario

Your income if exchange rate is needed must be from outside Thailand would would require Embassy letter and what they will allow to be indicated and if it exceeds the required 40k at current exchange rate.

They have accepted pre tax amounts before.