Can I extend my Non-Immigrant B visa for 30 days after my employer cancels it due to a job change?

You could also just get an extension based on marriage, which you can still get a work permit on. That way your visa or extension of stay is no longer dependent on your employment.

Just a little advice: DO not give YOUR passport and YOUR work permit to another colleague and hope all get cancelled. YOU signed for these documents and stamps and YOU will be held responsible if things go wrong.

DO IT YOURSELF, they can walk with you.

𝟭 - 𝗦𝗶𝗻𝗰𝗲 𝗜 𝗮𝗺 𝗺𝗮𝗿𝗿𝗶𝗲𝗱 𝘁𝗼 𝗮 𝗧𝗵𝗮𝗶 𝗰𝗶𝘁𝗶𝘇𝗲𝗻, 𝗜 𝗰𝗮𝗻 𝗴𝗲𝘁 𝗮 𝗼𝗻𝗲-𝘁𝗶𝗺𝗲 𝟯𝟬 𝗱𝗮𝘆 𝗲𝘅𝘁𝗲𝗻𝘀𝗶𝗼𝗻 𝗼𝗳 𝗺𝘆 𝗡𝗼𝗻 𝗜𝗺𝗺𝗶𝗴𝗿𝗮𝗻𝘁 𝗕 𝘃𝗶𝘀𝗮 𝗳𝗼𝗿 𝘁𝗵𝗲 𝗽𝘂𝗿𝗽𝗼𝘀𝗲𝘀 𝗼𝗳 𝘃𝗶𝘀𝗶𝘁𝗶𝗻𝗴 𝗺𝘆 𝘄𝗶𝗳𝗲.

not correct

you COULD get a one time 60 day "visit thai family extension" under this clause here

𝟮 - 𝗗𝘂𝗿𝗶𝗻𝗴 𝘁𝗵𝗲𝘀𝗲 𝟯𝟬 𝗱𝗮𝘆𝘀 𝗺𝘆 𝘃𝗶𝘀𝗮 𝘀𝘁𝗮𝘁𝘂𝘀 𝘄𝗶𝗹𝗹 𝗰𝗼𝗻𝘁𝗶𝗻𝘂𝗲 𝘁𝗼 𝗯𝗲 𝗮 𝗡𝗼𝗻-𝗜𝗺𝗺𝗶𝗴𝗿𝗮𝗻𝘁 𝗕 𝘃𝗶𝘀𝗮.

not correct and your status now isn't Non-B, you are on a yearly extension of stay based on employment FROM a Non-B visa you're not here on any visa any more at all

once you get the 60 day visit thai family extension you'd be on an extension of stay for that reason (visiting family), as the extensions were unbroken, it would track back to the extension based on employment and that would track back to an original Non-B visa

𝟯- 𝗗𝘂𝗿𝗶𝗻𝗴 𝘁𝗵𝗲𝘀𝗲 𝟯𝟬 𝗱𝗮𝘆𝘀 𝗜 𝗰𝗮𝗻 𝘁𝗿𝗮𝗻𝘀𝗳𝗲𝗿 𝘁𝗵𝗲 𝘃𝗶𝘀𝗮 𝘁𝗼 𝗺𝘆 𝗻𝗲𝘄 𝘀𝗰𝗵𝗼𝗼𝗹.

again not correct

you aren't on ANY visa, look at the stamp in your passport, it should clearly say "extension of stay permitted until" and have a date

that isn't a visa

Now, once you get the 60 day visit thai family extension, you COULD get the documentation together, and apply for an extension based on employment (because the only requirement to do that is that what ever extension you're on has to track back to SOME Non-Imm visa that allows employment and at one time you DID have a Non-B visa) even though you've been on extensions many years

The only thing you have to realize is that what ever immigration office you're dealing with to get the new extension based on employment may not allow you to do it once you take that 60 day visit thai family extension (although there is nothing in the rules that prohibits it and many people use that extension to "buy time" to get other

It's the immigration office where you'll be getting the new extension based on employment that will have the final say on whether you can go from an extension based on visiting thai family to one based on employment.

Nope, not correct. There is a 60 extension to visit Thai family, maybe that is what they meant.