When can I renew my 1 year non-B visa for Thailand?

as far as my experience, if you work in the same school or the company, they will extend your visa by completing some paperwork provided by the school/the company, and also they will extend your work permit on the new page of the same bluebook, or if you start to teach in different school but in same province , you can renew your non.b visa by paperworks from new employer without leaving country

According to this post

3/posts/4/

Your Non-B expires in December 4, 2021. At the earliest, you can apply for a one year extension of stay based on employment on Wednesday, October 20, 2021 (assuming 45 days) or Thursday, November 4, 2021 (assuming 30 days).

*SOME* immigration offices may allow a person to apply a little bit earlier, if they have an extremely good reason, but I doubt they would let you apply a month or more early.

What immigration office?

Chiang Mai, Bangkok, Buriram, Phuket, Chiang Rai and a couple other ones all allow people to apply for extensions when they have 45 days or less left on their current stamp.

Everyone else is 30 days.