Oh, sorry to hear. There are 2 kind of agents/agencies if you know what I mean. There is no problem using one if you can fulfill all requirements you need for y'r imm. Better go for the legal path, otherwise in future you can run into problems. Good luck !
Bit off topic but official it's called a NON Immigrant O. Then there are a lot of reasons you can choose. Most are for retirement or mariage. Nowadays it's always 'single entry'. (Before there was a multy entry, but think they don't have it anymore). So, this visa is valid for 90 days. If you come in in Thailand within de dates mentioned on the visa, you can stay for 90 days in Thailand. Most people with retirement (older then 50 years), buy this visa in their home country. And then go for a year extension (so no visa. visa is void/used) After you come in, try to open a bank account as quick as possible for sure if your Embassy not hand out an income statement (then you can use that with proof of 65k฿-plus each month). Then you put 800k฿ in that bank account 2 months before you go to y'r immigration. When you fulfill all requirements, you get the year extension. You have to repeat this every year. When you want to leave and come back in a year you need a re-entry permit before you leave to keep the year extension alive.
Also a "Certificate of Residence" from imm. you use, helps a lot for opening an account with the non O visa. The only thing I read that some imm. offices ( E.g. Bangkok) issues this only after a first 90 days report. So then you cannot get one there. Just ask the imm you gonna use for y'r year extensions. And for 2 separate bank accounts, with both the app installed, you could share the login data/pin.
What I read is that SOME imm. offices accept a total of 1,600,000฿ for 2 persons. But I think it does not have an advantage. This also if one should die, in Thailand, they can block the account untill it's clear who are the heirs.(e.g. family, married, a will).
Okay, existing users can still use the internet site with a browser but y'r right, maybe more will follow and stop using this. I still use the sites sometimes e.g. to make a print. With the apps (don't know Krungsri), making a screenprint is blocked. Also there are a bit more options on the browser sites, e.g. I can see the balance in my Fixed deposit account, which I cannot add in the app. I have Bangkok bank and Kasikorn bank. Hopefuly they continue a while.
No, not needed but maybe a tip. Check y'r airline for refund options. I bought a return flight from EVA Air and when I decided to stay in Thailand, I got a refund of 150€ !! on my 'return home flight', so this made my 'one way' to Thailand 150€ cheaper then when I had booked a one way ticket in the first place.