The M visa is not easy for us freelancers to get. But if you can show that you are actively working and provide links to your work it is possible. All applications are done through the MMOS website. Link and directions are here ->
The "enter before" date on the visa and the "admitted until" date you get stamped into your passport when you arrive are separate things. A re-entry permit keep that "admitted until" date alive. It does not add days or pause... only allows you to leave, return and stay to that date.
If you leave and re-enter a few days before the "enter before" date, you will get stamped in for another year.
So if your admitted until date is April next year and you buy a re-entry permit...as long as you return before That April date you are good.
Oh.. well I'm no expert but an expired visa is useless
A new Visa might help but getting one does not guarantee you will be allowed to enter Thailand. And you still have to be ready to show all the stuff I mentioned above.
Post a photo of the visa with the personal info blocked out. But guessing since the person didn't actually enter Thailand, the visa is probably still good.
Maybe a different Immigration officer will see it differently, they will for sure see that stamp.
I'd make sure you have the proof of onward travel, hotel booking and the 20,000 Bhat cash (or equivalent) ready to show the officer.