Visa on Arrival is for people who come to Thailand who need a visa but don’t have one already. You already have a visa. You don’t need it. They should stamp you in for your DTV when you come back in
Anonymous participant You don’t need evidence of LT stay in Vietnam. We sent in three days of hotel stay in Hanoi and that was sufficient. They just want to know you are in the country when you are applying. Also, make sure you send in your entry stamp from your passport or they will come back to you and request it which slows down the process
Not in the way you describe. My understanding is that you are only allowed one extension during the 5-year period. However, you can do as many border runs as you want, so as long as you leave every 180 days you can, basically, stay in Thailand for 5 straight years.
I just got approved in Hanoi with one fully confirmed appointment (with a formal confirmation from the hospital). I had made a second appointment on a different day, but had not been able to get a confirmation letter. I wrote a little cover letter explaining the situation, which may have helped, but in the end, one doctor's appointment got me approved.
One clarifying question: when you say “print the data page of the old passport,” do you mean just the pic/info page or should I have a copy of the initial DTV stamps as well?