What should I do to return to Thailand after my Non-B visa expires while traveling to Malaysia?

Regarding your second question, yes, you could come back in Thailand and get a visa exemption stamp (not a "tourist visa") when entering. If you enter on or after October 1st, you would get 45 days, and if you enter before that, 30 days. You can extend that for another 30 days for 1,900฿ at immigration in Thailand.

You could also apply for a Single-Entry Tourist visa at an embassy, which would give you 60 days and the possibility to extend another 30 days. However, you're allowed two VE stamps per calendar year by land, and since it's almost 2023, might as well use up your allowed VE stamps instead.

If you have an extension of stay, and are doing regular 90 day reports then you are not on the original visa, you are on an extension of stay for the reason of work. The day your work has formally stopped you must leave Thailand by the end of that day or find another way to stay in the country. On the other hand, if you are on your original visa (which is doubtful) then you can stay in Thailand till the validity of the visa expires. So, how long have you been working in Thailand? If more than 90 days then you are on an extension. And NEVER EVER hand your visa or work permit over to be held by someone, school, business. They are yours and must be with you.

Do you have a visa or are you on an extension of stay? I suspect the latter and the two are treated differently. If you are on an extension of stay that ends the day you stop working. You have to go and cancel your work permit AND your extension of stay on the day you stop working. You then have to find another means of being in Thailand be that a border bounce or whatever. If you have already stopped work you are technically on overstay.

If you do have an actual visa, as opposed to an extension of stay, you can stay until the visa expires but still need to cancel your work permit.

2 options. either get a re-entry permit and when you come back you will be stamped in until 31 Oct. OR just leave and enter on a normal visa exempt entry.