What should I do with my Non-B visa and work permit when they are about to expire?

I suppose that depends on the circumstances if you’re employment is finishing on the same date as your work permit then you must leave the country immediately and both you and your employer must inform the Labour department and Immigration, if your employment is being extended you renew your work permit for one or two years and then reapply for your extension of stay based on a non b Visa

Two scenarios, two different answers I hope this assists

PS on the cancellation of your work permit some immigration officers may extend your stay for seven days to put your affairs in order. Some won’t the rules are you must leave within 24 hours subject to permission from Immigration. 



You can not apply for 7 days, it is only given by courtesy of the Immigration officers, if a special situation has occured.

And you will know in advance, that you work would soon finish, and can act on that.

Yes you need to inform both the labour office and immigration which can be done prior to your last day at work.

Failing to inform immigration and the labour office can effect your ability to get another long-term visa and/or work permit in the future and will likely result in an overstay fine from immigration if you do not cancel your extension.

You're not on a visa, you're on an extension of stay which needs to be cancelled. Easiest is to get a letter from your employer stating your last day of work and using this to cancel both your work permit and extension of stay in advance. Then you simply leave by the date in the letter