the easiest way to to go to Savannakhet, upon your arrival and get the One Year Multiple Non O. This gives you the flexibility to go out and in, every 90 days.
they allow two land border entry. For a quick border run you will get the "day pass" to stay a few hours there. Easy. Stamp out of Thai, walk across, stamp into Myawaddy, nowadays they prefer THB500, after an hour or so back over the bridge . stamp back into Thailand, no question ask.
first timer might not be asked, but for second time or back to back they will ask Bank Account THB 200.000.-. If you need a yearly without proof of funds go to Savannakhet.