Can I convert my Non-B visa to a tourist visa while remaining in Thailand?

That you want to stay doesn't mean you can,

So let's answer your questions

𝗣𝗹𝗲𝗮𝘀𝗲 𝗮𝗱𝘃𝗶𝘀𝗲 𝗶𝗳 𝗜 𝗰𝗮𝗻 𝗰𝗼𝗻𝘃𝗲𝗿𝘁 𝗺𝘆 𝗡𝗼𝗻-𝗕 𝗶𝗻𝘁𝗼 𝗮 𝘁𝗼𝘂𝗿𝗶𝘀𝘁 𝘃𝗶𝘀𝗮 𝘄𝗶𝘁𝗵𝗼𝘂𝘁 𝗹𝗲𝗮𝘃𝗶𝗻𝗴 𝘁𝗵𝗲 𝗰𝗼𝘂𝗻𝘁𝗿𝘆

Nope you can't get a tourist visa inside thailand.

𝗼𝗿 𝗴𝗲𝘁 𝘀𝗼𝗺𝗲 𝗸𝗶𝗻𝗱 𝗼𝗳 𝗲𝘅𝘁𝗲𝗻𝘀𝗶𝗼𝗻

you go to the immigration office that issued your extension and you cancel it and then you immediately apply for a 60 day covid extension for 1900baht

𝗔𝗿𝗲 𝗯𝗼𝗿𝗱𝗲𝗿𝘀 𝗼𝗽𝗲𝗻?

Land borders are NOT open for exiting thailand but you can fly out and back in

𝗗𝗼𝗲𝘀 𝗟𝗮𝗼𝘀 𝗿𝗲𝗾𝘂𝗶𝗿𝗲 𝗾𝘂𝗮𝗿𝗮𝗻𝘁𝗶𝗻𝗲 𝗼𝗻 𝘁𝗵𝗲𝗶𝗿 𝘀𝗶𝗱𝗲 𝗶𝗳 𝗜 𝗱𝗼 𝗵𝗮𝘃𝗲 𝘁𝗼 𝗴𝗼

that is NOT a thai visa question but the country Lao is closed to foreign entry by air or land for all practical purposes

𝗖𝗮𝗻 𝗜 𝗺𝗮𝘆𝗯𝗲 𝗴𝗲𝘁 𝟯𝟬 𝗱𝗮𝘆𝘀 𝗼𝗻 𝗲𝗻𝘁𝗿𝘆 𝘄𝗶𝘁𝗵𝗼𝘂𝘁 𝗵𝗮𝘃𝗶𝗻𝗴 𝘁𝗼 𝗴𝗲𝘁 𝗮 𝘁𝗼𝘂𝗿𝗶𝘀𝘁 𝘃𝗶𝘀𝗮 <- you would have to FLY out of thailand, meet the entry requirements of a nearby country, and then meet the entry requirements to come back in to thailand.

𝗜𝗳 𝗜 𝗵𝗮𝘃𝗲 𝗮 𝗵𝗼𝗺𝗲 𝗵𝗲𝗿𝗲 𝗱𝗼 𝗜 𝘀𝘁𝗶𝗹𝗹 𝗻𝗲𝗲𝗱 𝘁𝗼 𝗱𝗼 𝗮 𝗵𝗼𝘁𝗲𝗹 𝗾𝘂𝗮𝗿𝗮𝗻𝘁𝗶𝗻𝗲 𝘄𝗵𝗲𝗻 𝗜 𝗰𝗼𝗺𝗲 𝗯𝗮𝗰𝗸 𝗶𝗻𝘁𝗼 𝗧𝗵𝗮𝗶𝗹𝗮𝗻𝗱

If you're vaccinated you do a Test&Go (one day in a hotel until you get your covid test results) doesn't matter if you have a condo, house or what ever you meet the entry requirements to get into the country.

I'd say go cancel your current extension based on employment and try to apply for the 60 day covid extension, you'll either get it or they'll sell you a 7 day stamp that gives you a week to get out of the country. 😮

If you have more questions about getting IN to thailand post your questions on this group