What are the procedures and timelines for canceling a work permit and visa in Chiang Mai, and crossing a land border the same day?

Given the new rules i've been reading about, that you must cancel work permit AND work visa THEN leave the country on the same day, does anyone have any experience doing this from Chiang Mai and reaching a land border on the same day?

Mai Sai would be the closest border -- actually 5 hours by bus from CM... Does anyone know when the border closes?

Another option would be Vientiane... It might be possible to fly to Udon Thani and make it over the border there in a single day... Does anyone know when the VTE border closes?

>> it would be preferable to go to the burmese border to avoid paying for a 1 month Laos visa. If going to Laos, may as well stay and request a 60 day tourist visa, as opposed to a 30-day visa exempt (although I hear you have to get an appointment these days!!)

>> alternatively, does anyone know if the authorities will charge a 500 baht overstay if you leave the country the day after you cancel the visa?

THANKS ALL FOR YOUR ADVICES