Can I do a border run to Mai Sai for a 30-day visa exempt after extending my METV?

Hi Guys, I'm about to go to immigration and extend my last METV 60 day entry (gained on land entry at Mai Sai in January 2020 - METV visa now expried), which should take me to mid April if they extend for 30 days.

Now I may require to stay on another month it two after the extension expires. I'm assuming that as I've only done one land entry this year, I should be able to do a border hop again at Mai Sai in April and get a 30 day visa exempt, which I can extend again in Mid May all going well. My concern is that I will have been in Thailand over 7 months in April and worry that they may not let me back in to Thailand. My questions is: If I go to the border say 1 week before my extension expires, will they allow me to leave over the border if they are not intending to give me a 30 day visa exempt and allow me back I to Thailand. I'm thinking, If they inform me before I leave Thailand over the border that they wont give the visa exempt, at least I will have a week left on my extension to tie things up. If they don't inform me before hand, I would be trapped in Myanmar and all the hassle that would cause Sith all my things back at my hotel. Sorry for bei g so long winded but I thought I'd give all the facts. By the way I'm from UK and have a long history of METV but mostly just stayed a few months in previous years. Your advise would be much appreciated.