What is the current situation regarding multiple entry visas for Thailand, particularly with travel restrictions?

Yep, sadly (for most people right now during this covid shit show with the neighboring countries and land borders closed) a year long, multi-entry Non-Immigrant Type visa (any type) is about as worthless as tits on a tomcat :O

There's just no cost effective way to bounce out and back to get another entry stamp on one without quarantining in the country you're going to and/or quarantining here when you come back in.

Right now you're only options are in country extensions based on the reason you got the visa or one based on the inability to travel due to covid.

Now it remains to be seen when/if the land borders and neighboring countries will re-open so that people can bounce out and back but at this time that is not a viable option for most people

Borders being closed sure screwed up using a Non O or Non B Multi-Entry in the manner it had been used for many years. I preferred it over a B Extension mainly for the reason of not having to deal with Immigration at all. Maybe someday....

How the visa is treated has not been changed at all. Same to before. With a multiple entry visa (not with A or X), you have to leave Thailand within 89days on every entry.

Yep and with COVID and all land borders closed... They are worthless unless you are a worker (oil field and crew on ship..business... etc ) coming and going thru the year with added need to meet CoE entry requirements each time.

It's a non starter tbh...