What visa options are available for a person returning to Thailand after living abroad for years, particularly concerning family and financial requirements?

I have a friend who went back to the UK to work, but hasn't been able to find stable employment and so wants to get a visa and return to Thailand so that they can be with their wife/children. They aren't very computer literate or visa savvy, so need a bit of help.

- They were previously here for almost 10 years and have a wife (Thai) + children in Thailand, however have been out of the country since November 2018.

- The Glasgow consulate in Scotland is their closest consulate, so the one they'll likely use.

- They will have a 1 way ticket, but can get another ticket for proof of onward travel. However they were here for almost 10 years continuously in the past, and immigration seems to have been cracking down.

- They won't be able to meet any financial requirements for visas (Not even 20,000 THB cash for tourist visa)

- They usually get a multiple entry O visa based on marriage/dependents from Savannakhet, but don't know if requirements in the Glasgow consulate are different (And their wife usually does it for them, so a list of the documents required would be great).

- All of the documents they usually use for their visa are in Thailand. They can get copies scanned/e-mailed, but no originals or copies signed by their wife (Although can use snail mail if needed I guess).

- They are over 50, so eligible for a retirement visa provided they don't need to show any funds. Would this be a viable option?

Thanks for any/all assistance.