I have seen posts from competent people saying that only one of the 60 day entries can be extended. But this may depend on the Immigration Office you go to.
And such a Non B would soon run into problems in Thailand when no WP ever showed up. Once upon a time people could wander around Thailand for a year with a Non B not connected to a WP but those days are gone
Non Imm B Visas are connected to a Work Permit. And 99% of the time the Work Permit is assigned to one Employer - one location - one job. Generic B Visas and Work Permits do not exist in Thailand