Does Thai Embassy in Vietnam allow to apply DTV visa for the people who are on Vietnam’s tourist visa?

I'm currently I'm Thailand on a Non-O visa based on marriage to a Thai national. I am planning on going abroad soon for the first time since coming to Thailand 3 years ago, but I don't know how long I will be gone. When I was at immigration they I requested to see the form to apply for a multiple entry visa, in it they request that you state the day of departure and they day of return, however I don't know yet when I will return because I want to stay flexible. I want to get a 90 day tourist Visa for Vietnam and check out the country, however in case I don't like it there or something comes up I want to be able to come back to Thailand sooner. What should I do in this case?

Hello, what is the procedure for a tourist visa in Vietnam.

3.4 Evidence of transportation

Flight itinerary for ROUND TRIP ticket (in Thai or English)

Flight reservation/itinerary must show the applicant’s full name, arrival and departure’s date and time, and flight details

I'm travelling from Bulgaria to Bangkok without entering Thailand, then I go to Vietnam...

Should my round trip ticket be to Bulgaria,Vietnam, or anywhere out of Thailand?

I've been to Laos and is much easier, but they don't have appointments the next 25 days

In early 2020 Vietnam announced that, wef July, the tourist visa would be limited to 30 days with no extensions thereafter. Then covid struck and the country locked down. With the reopening, is the ‘no extension’ rule enacted, or has it been waived?

Thinking to go to the Ho Chi Minh embassy in Vietnam to apply for a single entry tourist visa. How strict are they with previous visas? I know they are strict with the documents required, bank statements, flights etc. That is fine. Just wondering how they are with previous visas.