I personally wouldn't take a chance. Once you get through immigration on the Burma and Thai borders you still need to catch a songtow back to the bus station... our songtow was stopped a couple of times by the police checking id's....
Our bus arrived an hour later than expected and we had about an hour to spare... we would have missed the 2:30 bus.
Also, I highly recommend that you pre-purchase your tickets a few days BEFORE you leave... our bus was fully booked
I did this border run on my METV last week. I was not required to show proof of funds, onward travel or lodging. It was a fairly quick process. I took the 8 am bus to Mae Sai and the 3:30 pm bus coming back.
I received my METV a few days ago from the Consulate in LA. They require proof of onward travel and proof that you will leave the country multiple times during the 6 month period. I'm retired so I provided proof of my retirement... they are VERY strict... you can send a message to the consulate via FB messenger...they are very responsive...
It's a super quick process provided your paperwork is in order. I dropped my paperwork off in the morning and my Visa was ready at 3 PM that same afternoon