Irish passport holders are not eligible to pay for a visa on arrival as they enter visa exempt, for free (currently 45 days) if they haven't bought a visa in advance.
Is it necessary to do this? I moved to a new province 9 months ago, and 2 weeks ago renewed my annual tax with the insurance showing my new address, and it was processed as normal.
The prepaid envelope is one of the reasons it's easier to do while in the UK. When I did it (in 2016) the Thai Embassy wanted payment with a £10 postal order! Hopefully that's no longer the case.
It's all covered here if you want to do it yourself. Much easier to do if you are in the UK yourself, or have someone there to do it for you. The Legalisation Office in Milton Keynes, will forward the legalised document on to the Thai Embassy in London for you, if you have a pre-paid envelope. It took about 14 days to get mine done.
She doesn't need a visa for Thailand. As a US citizen she'll get 45 days visa exempt (if she's arriving before March 2023). She can buy a Visa On Arrival for Laos when she goes there, and then another visa exempt stamp when she comes back to Thailand.
My British son has lived here since he was born and he's 7 now. I extend his Extension as my dependent every year and never once has there been a problem with him not having done a 90-day report.
I was in Bangkok recently and never wore a mask and noticed quite a few Thais doing the same, even on the BTS. Until people start doing the same it will take ages to change people's mentality, although I have no problem if they wish to continue to do so.