Can I enter Thailand with a tourist visa while my DTV is still in process?

I did it. My application was taking longer than the advertised processing time. I had responsibilities to get back to in Thailand. I re-entered Thailand on a visa exempt. A week or two later, my DTV was approved. I did a quick border bounce to get on DTV status. Had no problems. This was back in May.

Yes

Do not leave the country you're applying for. They may ask for a copy of your passport with ALL pages or call you in for an interview.

That's why they ask for proof of location. You must stay there until approved

Don't do it. With TDAC the consulat might have access to your Thailand entry data. I remember a case when somebody entered Thailand during the application process and instantly got an invitation for an interview for the next day

I’m reading through all the comments and disagreements here, and it made me think of a hypothetical situation. What if someone has to enter Thailand urgently—say a parent becomes seriously ill and needs immediate care—while their DTV application is still pending? And let’s say the DTV actually gets approved while they’re already in Thailand.

It seems completely reasonable that people might need to enter Thailand for all kinds of legitimate, time-sensitive reasons, even if their DTV isn’t approved yet. In that case, they’d obviously have to leave and re-enter with the newly approved DTV, which makes perfect sense. But denying someone entry just because their passport shows they entered Thailand while waiting for approval feels unreasonable. Can anyone actually point to an official law or regulation that says someone will be denied entry simply for entering Thailand while their DTV is pending—even if they later leave and re-enter properly with the approved DTV?

Nope. You can’t. Plenty of embassies have warnings about this on their websites. They may ask for proof of your location, photos of every page in your passport, and even an interview. If they find out you entered Thailand during the process, you’ll be denied. Did some people manage to do it? Yes, but others got caught and lost their fees. There will still be a record of your entries in the immigration system, and the date of issuance of your visa is also listed. If immigration ever wants to play with you at the border, they can.

Guidelines state you need to stay in the country you apply from.

Doing otherwise risks your DTV application to be rejected.

You can come to Thailand and enter as you wish. Can you get the visa cancelled if they find out ? Possibly. Can you get away with it and re enter once you get the DTV? Possibly. But is it worthy he risk to have the risk of your DTV cancelled.

Where did you submit ?

You cannot. You can probably get your application botched by doing so.

You are supposed to stay where you are applying

you can do whatever you want in life, what are the repercussions of your actions you will have to study