they posted a video on line following a tik tok video where the woman complained about having to show 20,000 baht in visa exempt - again this was a recommended by them to use airports and not same day - but as I mentioned people have posted no issues doing same day land crossings with DTV
You can do in country extension but its like doing the application process all over again :P have to verify everything again - its alot easier to just leave and come back - if you are worried about flight issue cancel the flight leave the country on Land then buy a ticket back i wouldnt recommend say day - according to immigration they are asking people to come back by airport not land crossings
Edit *** I have also seen posts in here where people do same day land crossings and had no issue
Tdac.go.th is free all arrivals non thai passport holder or perm resident, fill out 3 days before arrival - if your passport qualifies for visa exempt you can get 60 days no fee - just make sure you have 20,000 baht on hand or your currency equivalent and may need onward ticket - return ticket