Does anyone have experience cancelling their work permit and non-b visa before leaving Thailand to apply for DTV? Just wondering the process and timing of the steps. Thanks!

I am resigning from the current job, due to HR vacancy my company asks me to cancel work permit and non-B visa by myself and they said they will provide any document that I need.

I have 3 questions here；

1. How to cancel both of them？my location is at bangkok.

2. Can I apply covid visa on the same day I canceled them？

3. If I want to work at another new company, changing work permit and apply new non-B visa/or/holding covid visa and apply new work permit and non-B visa, which one is more easier？

Please kindly give me advice or share your experience here, thanks in advance!