not possible, Vietnam has electronic application. Takes to much time. Border run. But in reality they are not going to do anything for 3 days. No stamp just a fine of they wish to. I had over stay for week and immigration officer laughed and said they love making extra money. Paid a small fine no stamp. He said over stay is no serious under 30 days.
It's the game of thailand.csnt do one without the other. Need bank for visa and visa for bank. It's to force you into the agent route. Just surrender to the stupid games. There is no national standard to their own rules. Just pay the agent.