Jump in a minivan and go to vang vieng. That's what I did. Got an email for the interview went back the next day and approved before I even got out of the compound.
The green bus goes from chiang mai arcade.it takes about 5 and a half hours and they will drop you off at the junction for the border where there will be som tuk tuks waiting for you. Not sure about getting back the same day.
it was just called mergepdf, someone else recommended it here. I can't remember the limit size of my documents but it worked first attempt. Good luck 👍