I would imagine so if you have enough time on your visa. It took about 10 days to receive my passport back from the u.k. They kept me updated from start to finish.
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.