if you look specifically under the Non-O Retirement option it says this... "Copy of a permit of stay or other evidence to prove that the applicant is legally residing in Italy / Cyprus / Albania / San Marino (only for non-Italian / Cypriots / Albanian / Sammarinese passport holders)
You can get a 90 day Non-O Retirement visa in Italy only if you are a legal resident of Italy, take a look at the website for the Thai embassy in Italy. How old is your adult son, normally they cease to be a dependent at age 20 as far as Thailand is concerned.
You are not in transfer if you have to go through immigration and you require a visa to enter Thailand then you need a visa. What passport do you hold?
Once you are in Thailand and have 30 days or less left on your current stamp you go to immigration for a 12 month extension of stay but note you will need funds in a Thai bank for 2 calendar months before you apply so you need to get on with opening a bank account soon after arrival
what nonsense. I may be out in the sticks but I still like to enjoy life too. A meal for 2 at a decent restaurant is around 1000 baht, I run a car, I travel, I drink, I smoke. It soon adds up my friend
For life in bangkok I'd say $2600 USD per month is fairly meagre unless you don't get out much. I live out in the sticks and spend around $2000 USD every month, which also matches the income requirements for a Non-O based on being over 50 if you bring in money every month for your extension of stay