the DTV or the OA are not the correct visa, she should follow the Moderator's (Brandon Thurkettle) advice to apply for the Non-O visa, and stop quoting the wrong information her sister has given her.
I went to the AIS shop in Terminal 21 in Bangkok. I explained what features I wanted, and that I wanted a monthly plan that I could easily top up. They sold me a 300b / month plan that gives me 5G unlimited data (I think) etc. I go into my Bangkok Bank app and periodically top up my AIS account with a transfer. They send monthly reminders when they are about to bill me, and I can call a number and it will show me my current balance. Given your name, I assume you live in Buriram like me, I go to the AIS shop in Robinsons if I have questions or need assistance with something. I note that 5G is not widespread in Buriram.
I have every intention of staying on the 800k option. I came to Thailand to relax and have a good time in this wonderful country. I only have to worry about my visa when the annual anniversary comes around for the extension. The bank statement is a breeze because the 800k sits in a separate account, and the only transactions are the interest and the withholding tax entries. They produce the required letter in probably 5 to 10 minutes.
the reason I posted was that there was an implications that he needed the 800k and the 65k. As you know, you only need to do one of these. I have heard of people dropping down to the 400k, but then struggling to get back up to the 800k. They treated the 400k they took out as free money and spent it. Personally I prefer to just leave the 800k, and wear the extra loss of interest. I never have to worry or even consider the 800k, it just sits in my visa account. Personal preference.
you don't need the 65k monthly international transfers, if you continue to use the 800k option. You simply transfer what you need, when you need it. Yes, no need for agent.