In theory you should wait in the country you apply from until approval. Some have managed to do what you propose and got away with it. Others have been rejected because they did that.

Once approved it doesn’t matter if you enter Thailand from Country A, B or Z.

Depends on the office but an example for Phuket is at least 15 days prior. Up to 45 days is allowed there.

That said you’ll find it incredibly difficult to get an extension. Immigration don’t want to issue one so they will come up with all sorts of roadblocks to stop you applying.

99% of people find doing a border bounce is the better option.

Of those that have been successful in getting an extension my guess is 99% of those won’t bother to do so again.

I’ve not heard of any other office having this requirement. Doesn’t mean that there may not be one but I’ve never seen a post about one

Nope. You don’t. Bangkok used to have a restriction of having to have done a 90 day report before you could get a residence certificate but that policy stopped quite some time ago.

A 90 day visa is a non immigrant visa. They are only extendable for a year if you meet the requirements.

A tourist visa is valid for 60 days but then so is a free visa exempt entry if your passport qualifies. Both are eligible for a 30 day extension (for most countries).

You wouldn’t qualify for spousal visa in the sense that one of the spouses isn’t Thai.

No. The extension is based on the initial visa, so mandatory insurance would be required.

The only way to get “off” a Non OA is to leave when it’s over and either get a Non O from a local embassy or enter visa exempt and convert in country.

Perhaps it would be best to state where you are in Thailand.

Purpose of travel is “ visit family”. Leave the departure fields blank. Don’t even click on them or they become mandatory

1. Yes you can change dates.

2. Will depend on the officer but usually just your passport, copy of DTV and your last boarding card

3. Each entry you get 180 days. In theory you can extend once but in practice immigration will make it really hard to do so it’s easier to bounce out and back.

If you’ve stayed for 90 consecutive days in Thailand you need to report to immigration. Each office will have slightly different requirements but it’s usually pretty quick to do a report.