Do I need to renew my Non-B visa while my PR application is being processed, and how does it affect my child's dependent status?

Did you go out and talk to the people at the PR section at Chaengwattana (Section D) long before you're going to turn in your documentation?

I believe they would have told you that you should keep your Non-B extension and dependent child extension during this process.

post on the Thai Citizenship group and ask. Hands down that is the best group about Permanent Residence and acquiring Thai nationality on the inter-web today

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1.) Thai PR Applicants (who have their Thai PR applications successfully Accepted by the Thai PR Desk) do get 6 months Under Consideration Stamps ('Extensions') by the PR Desk, only after specifically requesting such, but the Thai PR Desk is usually expecting Thai PR Applicants to continue on their current Visas/Extensions (usually Non–B) as PR Applicants need to have active, current Thai Work Permits (WP)

2.) However, it will be some time before a PR Applicant will know whether their PR Application is Accepted and months, years (unknown currently) whether you will know if a Thai PR Application is successfully Approved and actually Receive Thai PR

3.) if a Thai PR Applicant has dependants piggy-backing on their current visa/extension (trailing kids/trailing spouse), then they (those dependants) will NOT be able to get a trailing kid/trailing spouse visa/extension based on those 6 months Thai PR under consideration stamps =

You have to continue with your current Non–B visa/extension in order for your dependants to continue with their trailing visa/extension

2 things worry me about your post, firstly, I have never heard of pr applicants getting a 6 month extension after applying, I only read that you must maintain your current unbroken extensions. Secondly, very slim chance of getting your pr in 6 months, also hurry, because the application window closes this year on 15th of May.