If you apply through the embassy/consulate in your passport nation, you could just upload the ID-page of your passport. Also driver license, utility bill or bank letter with your name and address. None of this in fact proves that you stay where you apply, but they can ask you to upload your last stamp or all passport pages including blank ones too, and in the end you’ll need to start your trip where your visa was issued.
The London embassy is otherwise known to be very effective with a two-three days processing time for visas.
This is not correct. Everything has become more strict now and people are getting questioned and even denied on their second attempt only after maximising one visa exemption.
This visa is valid for 180 days and gives you 60 days each time you enter Thailand which also can be extended with additional 30 days at your local immigration. So you’ll need one border bounce, but you have a way more safer basis for your stay which now is covered with a visa.
if I were you I would have applied for a six months multiple entries tourist visa (METV) through the Thai embassy in your area before I left. Then you’ve covered your whole stay with a visa and don’t risk to be questioned or denied your second entry.
You apply for a visa based on being married to your Thai wife for ten years and you will be travelling with her. I would ask my in-laws to confirm that you, as their son-in-law, came with their daughter to stay with them at their address in Ubon. (In the first place).
If you book a hotel with a confirmed hotel booking you don’t need an invitation, but sometimes if you give a private address for accommodation they will have a verification from the owner that you can stay at the actual address. So just asks them to write a letter confirming this with their telephone number.
As i read the website in Rome, you’re allowed to apply in Italy on a regular visa as a Schengen visa. Only the regular group of nationalities (Africans etc) requires additional documentation and processing time. (Don’t know if you meant anything else by "legal resident"?)
Most embassies allow foreigners to apply for visas online through the e-visa portal while they temporarily stay in their area. Definitely the best option to apply for a Non O visa outside Thailand and you can use your home bank account to qualify.
Processing time for a visa varies and you should check the website or contact the relevant embassy regarding this.
The website says up to 14 days processing time during high season.