The bank book isn't a problem. I applied for my Non o married to a Thai whilst in UK and got it back in 2 weeks. I was asked for a letter from the bank who I guess guarantees you have it,as the print out from the bank wasn't what they want (even though the bank manager said he knew exactly what I neededπ ) I think it was made easier the fact I'd already entered Thailand on a non o as I believe people have had issues changing from different visas, especially the over used 'Covid Extensions πIts easy enough to apply for the non o from uk imo. For uploading the ID'S of partner use a free collage app as when uploading multiple images on the evisa site it only gives you impression you can upload one. They accepted my collage of about 6 different images on 1 image file. Good luck
Also, I'm filling in the TM8 form as well for when I go back. It asks where my previous visa was issued. I got my non o visa from the Thai Embassy in London. So as I'm 'extending' would I put London. As I would have already been given the 'extension' here in Khon Kaen?