correct. My employer went to the MOL and cancelled it and gave me the cancellation slip too late in the day to visit imm. Water under the bridge but lesson learned!
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!
A non imm B visa is not an authority to work per se. It is required before a work permit(wp) can be issued by your provincial labour office. An alternative to the B is a Non Imm O based on marriage to a Thai national. I worked on a WP for 9 years and never left - I extended annually at immigration. Having had a 5 year gap I am doing it all again.