If you don't want complications, you can leave Vietnam or Malaysia for at least 2-3 days and then return by ordering a green corridor, Fast Track, for secure entry. With this option, you won't be asked anything at the border and will receive another 180-day stamp.
A DTV visa is classified as a tourist visa, so you may be asked for a return ticket, cash, and a hotel reservation. Therefore, you should be prepared for this. If you are unsure about anything, it's best to book a fast track meeting with an officer.
Your account will remain open until the first verification from the bank, for example, to update personal information or visit the bank for some services. It doesn't matter when the account was opened; what matters is what visa you currently have. A DTV visa is not a long-term visa; it is a tourist visa.
You need a TM 30 certificate; it will be issued to you based on where you will be residing. The property owner must provide rental documents. With this certificate and your passport, go to immigration the first time and submit a 90-day report. This is form TM 47. Next time, you can do this online on the immigration website. No need to go to the office.