There's no connection between you having been in Thailand for 2 weeks on a visa-exempt entry stamp and your DTV application. Just make sure that you don't overstay before leaving Thailand and applying for the DTV.
Intended arrival date has either passed or is imminent: I would contact them, politely asking if there is a problem or if they need anything, mentioning your travel plans. There's no way to know how they work, so it could mean anything that they're late, from having concerns and checking carefully the application to the application having gone down the drain, and everything in between.
What did you mention as her intended date of arrival? Do they mention an average processing time on their website?
You can try to contact them, since it's been a month already, as long as you've been waiting longer than their processing time. Depending on the embassy/consulate: by e-mail, phone, messenger, line...
Adnan Khairi In the US it's normal, I have heard. Not in my home country, a EU member country. I have never been asked a single question by immigration officers. The most they have said is "welcome back!". What should they ask by the way? For example, why I am coming back to my home country? Does it make any sense? Or where I have been? What does it make for a difference?
Which channels of communication did you use? Do they have Messenger? Some embassies/consulates do not answer e-mails/phone calls, but they answer on Messenger.
Participant(e) anonyme YES IT COULD. Just contact your bank. There's no certainty, but it could well be the issue you are encountering. Give it a try, instead of waiting.