Do I need to leave Thailand with a DTV visa or can I extend my stay at the immigration office?

Yes. Called a border bounce. You leave by air, land or sea, and return. No timeframe on how long to stay out. Some land borders you walk across and come back some air flights you land check in to x country and get on the next flight back. Many use the time to have a short vacation in whatever country they’re heading to.

@Marion ***

yes, leave and return

Marion Gs actually, visaruns" are allowed, they are even recommended by Immigration. That is if your aim is to apply in the neighbour country for a Non-Imm-O , Non-ED, Non-B or any other visas like the DTV. On visa-exempt entries, nobody ever did a visa run, that was a misconception by Immigration when their new approach got published last year. They actually meant "consecutive visa-exempt border runs" which they wrongly named "many visaruns"

Marion Gs yes, exit, stamp in somewhere else then exit and re-enter Thailand, it can be that simple (but bear in mind that a visa may be needed to enter the chosen country).

Marion Gs The difference between a "visa run" and a "border run":

There are two things travelers can do:

EITHER

You do a "visa run"... A "visa run" is pretty self-explanatory.

You visit a Thai embassy or consulate in a neighboring country and apply for a Thai visa through their online e-visa system.

Many more people do this every day than you might think, for example, those applying for a Non-Immigrant ED visa, a Non-Immigrant B visa, or for a DTV visa.

It could be a neighboring country of Thailand or any other country you can reach by air to use its embassy to obtain a visa.

OR

You do a "border run"... A "border run" or “border bounce” is pretty self-explanatory (if you consider what you're doing at a border).

You go to a land border, leave Thailand, and enter the neighboring country. You either enter the neighboring country visa-free, or you have to buy a visa on arrival (for example, for Laos, it depends on the country and its entry requirements.

Then you either turn around and re-enter Thailand, or you take a short vacation in that country before returning to Thailand for another visa-free entry and a 60-day stay.

OR you have a valid multi-entry visa, which allows you to activate another stay permit period upon re-entry, like the DTV.

A border run and a visa run can be done by air, sea, or land.

Most of these transport companies, which bring people to the border and back, and which occasionally also transport people to embassies in neighboring countries, call both procedures "Visa Runs" and themselves "Visa Run Companies."

This is simply a case of using the same term for simplicity, but technically it's not accurate.

You're always doing a Border Run with a "Visa Run Company"—not a Visa Run.