Seeing as the departure is not until late January, it leaves them plenty of time to acquire a turist visa from the nearest Thai embassy. That would both be the cheapest option (while avoiding overstay), and they would not have to spend potentially a whole day of the holiday in an immigration office to extend their 30 day visa exempt.
you could get a multi entry turist visa before going to Thailand. That would get you almost 9 months of stay in total, after which you could go to a nearby country and get another single entry visa for 60 days and extend another 30.. Or you could get either the single or multi entry before coming to Thailand, and then before that expires, apply for a one year extension at immigration based on being the guardian of your son. I believe that would require 500.000 baht in a thai bank in your name, I dont recall how long it has to be seasoned, but i am sure others here can tell you that.
Gregor Huettner atm card is not needed.. why do you say this? Just have the bank letter that states the account is yours, and what amount was in it at the time of the letter being written, together with the bank book and copies of the last few months from that book. (
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months depending on what kind of extension)..
Not all accounts have an atm card, and I have personally never heard of anyone anywhere having to use an atm card to prove a bank statement for immigration.
if you are able to make the 30 extension more than once on your METV is up to the officer at immigration. There has been some people reporting they got refused more than a single extension pr visa
if your METV is still valid when you return you will get 60 days that can be extended by another 30 days at immigration. If not annika is right, you wil get 30 days and can extend that by another 30.. Its not possible to make more than one 30 day extension on each turist visa entry.