You would not be renewing your visa at an embassy/consulate, you would be applying for a new one.
Chances are you would be refused another Non-B as they would tell you to extend your permission of stay in Thailand.
Your employer should help you with all the paperwork for the extension,and so while it may take a day of your time, it would give you a years stay.
Hundreds of people every day use CW for employment extensions, they seem to cope, I am sure you would too.