What visa? A tourist visa? You can extend tourist visa and visa exempt by 30 days at nearest immigration office. If you already did it, I suggest you wait closer to November 17 to leave. Are you married? If so, yeah, go to Savannakhet around November 15 and apply for 90 days Non-O (they are not asking for 400k baht). And then you can extend 60 days at immigration office near when the 90 days expire.
For now, thankfully, single entry Non-O based on marriage at Savannakhet doesn't require 400k. It give you 5 months (60 days family extension), so not too bad. My friend will be in Savannakhet this Friday or Monday and he will try to pay the 13k baht bribe to get the Multi Non-O. Rumor has it that it's the current price with a "fixer/bribe".
You can't do the 90 days report online if it's your first 90 days report. It must be the case because 1 days late will not be denied if you try to do it online. You can do it online up to 7-10 days late.
It is single entry for support of thai child not multi that the person on ASEAN forum got (Ron is relying a picture, its not him). It says single on the stamp. You are right about the rest. The person on ASEAN forum forget to specify what he was applying for.
You can do METV in Finland (Multi Entry Tourist Visa) which give you 6 months and if you active your last entry at 5 months 29 days, you basically get 9 months. Or you can do 90 days Single Entry Non-O in Finland and extend 60 days later which total 5 months. Or can you do the same Single Entry Non-O but pay an agent around 25k baht to get yearly extension without needing the 400k baht. An agent can provide that for you in Thailand. It's bribery but stamp will be legit. There always a way to stay long term if you want to. It depend how long of a trip you want. Years? 6 months?
You can only apply at immigration not online. It's the same as applying for 30 days visa exempt. I've done it twice this year. I've done 30-30-60 (30 days visa exempt extendable for 30 days followed by 60). The reason for the extension switch from visa exempt to marriage so you can do both if married. Since the Non-O is based on marriage you can only do 60 days not 30-60. You need your wife blue book, id card and marriage certificate, and the rest is the same as visa exempt or tourist visa extension.
Can I see your stamp? The other one posted here from ASEAN was debunk by my wife for being based on "having a child", not for "marriage". Above the "USED" stamp there is a Thai sentence. Multi Entry for having a child was never possible in Savannakhet, only for marriage.
Fyi, my wife debunked this picture to me. On the top left (above the "used") stamp, it read: อุปการะบุตรไทย (in very old style). This refer to Non-O Single Entry based on having a child, not marriage.