Potentially, you have to align your planets to the day , I agree with Andrew ( hence why my original answer had no smart arse remark ) I used to use this Visa around 10 years ago , it was a pain in the arse frankly , and I used to Fly out of HH to KL ( it had that flight then ) and spend 3 - 5 days ..
They did not like the land crossing , which had been my intention , even back then .
hmmm honestly not sure Sam , I'd be pretty confident you could just get it here , I know , if using an agent anything can happen 5555 ..And there is a bit more to the marriage Visa , rather than retirement.
Yes , not uncommon , but just apply again and keep applying , add some more info as to why she MUST return , give them more than they request , you are a great chance of success second time around .
I think 20k is fine , it will be a one off , if you were using an agent it would be around 16k , and this is a qualified individual, it matters not the price in your home country , not even remotely relevant .
Just pay the money , get the Visa , consider yourself lucky , it's cheaper than leaving , and Sabai Sabai .
The only other alternative is to find a different country , but on your writings you will is to stay here - Just pay ! It's a cost of your stay , a Visa cost .
So ( as an absolute bare minimum) after transport and accomodation ( that's AFTER ) you need at least 10k baht per week x 4 = 40 k say plus 15k plus 10 = 65 k for an individual , now this is also the amount needed for you Visa , for 2 people , times it by 2 .