The best places to apply is from the embassy in your home country. Many DTV holders have been asked why they didn't get their DTV at home on entry. It will make future problems much less likely.
Otherwise I think Hanoi is still the most recommended currently.
There's nothing that "qualifies" you for a Thai bank account. There is no visa or visa type that does or does not legally allow a bank account. You will need to find a bank willing to open an account for you.
definitely have to have your own service with your own wired router inside your room. Shared building wifi does not have the service availability for the level of confidence needed for working.
I haven't worked in a call center, but I've worked remotely from Thailand and done lots of meetings with my co-workers in the US. I never encountered any latency issues that affected the call enough to make a difference. Both on and off VPN seemed fine in those cases. Sometimes there's a bit of lag when using apps and tools on the computer, but nothing more than a couple extra seconds when trying to load something.
if you're really worried you can save the money on a visa and put it towards a "safe entry" service with an agent. They'll meet you at the airport and make sure you get into Thailand through an arrangement with immigration. Starts at 2000 baht and goes up to 4000 or more if your past is really bad. They'll take all your passport information first and send it to their contacts at the airport before giving you the final price that's 100% guaranteed entry.
They can get one by mail to the AAA in the US but it will take a long time. Most DLT offices will require them to have an IDP in order to skip the test to get a Thai DL.