no you don't. You can get a bank account with a DTV and you don't need an agent. Just because some banks are not up to day on the process doesn't mean you can as many have for various reasons
you have no clue what you are talking about. DTV allows you to work remote, just not for a Thai company or Thai clients that's all!
Many reasons to have a Thai bank account. First to transfer money from your main account from your home country to your Thai account so you can use local currency easier
Setup direct debits and pay bills like phone and medical, rent etc.
Many people have opened accounts under DTV and visa except for medical bills.