If you have a work permit issued on a Multi Non-Imm visa, how does it work when you cross the border every 90 days? Is your work permit still valid? Do you have to go to the labour office to "renew" it? Is it "renewed" on the spot or it takes a certain time? Are there any fees attached to this?

You have to renew. Not sure if there is any fee.

If you have a work permit issued on a Multi Non-Imm visa, how does it work when you cross the border every 90 days? Is your work permit still valid? Do you have to go to the labour office to "renew" it? Is it "renewed" on the spot or it takes a certain time? Are there any fees attached to this?

Your WP is only ever issued with an expiry date relating to your visa. In this case.............90 days. Then it expires.

Do a border run before the expiration date on the Visa...........obtain another 90 day stay then report back to your local Ministry of Labour for a new WP with a new date to match your visa.

I forget how much mine cost...think it was 1000 baht. I waited 2 hours for mine to be renewed.

Other labour offices may take longer or shorter.