Do I need to cancel my work permit or my visa first when changing to an ed-visa in Thailand?

Beware, my WP was cancelled and I got receipt too late to go to imm that day to change from B to O. Got there at 0900 and had all the right stuff but still got charged 2 days overstay. Go figure!

Let's try to explain: You wrote that your inside of Thailand on an Extension of Stay. That means you are NOT inside of Thailand on a non immigrant Visa it is one or the other. You bought the Visa at a consulate or Embassy, on entry they put a stamp or wrote: USED on the visa, from that moment is is invalid and just a memory in your passport and before the last day of Admitted to Stay date you went to Immigration to apply for an Extension of Stay based on working. The day you go cancel your Work Permit you also visit Immigration Office and cancel your Extension of Stay. Than you leave Thailand and apply for the Visa of your choice if you meet the requirements.

singapore does NOT do walk up visa applications anymore. It's all done online, you scan and submit your documentation to them and they email you when your application is approved and when you can go there to get the visa.

And by this link you can apply even before you leave Thailand:

Singapore is very nice, here you can read the requirements of getting the Non Immigrant ED Visa:

@Patrick ******

, are you on a VISA or are you on an extension of stay that you got from the immigration office ?

you cancel your work permit, then take that receipt and documentation from your company to the immigration office and cancel your extension of stay.

IF you are still on the original entry from a VISA you don't cancel it and you can stay until it expires.