Why would you leave a job in BKK with work permit, to change to DTV? I’d find it suspicious too.
I also did my DTV in Taipei after working in BKK for 5 years and they were very suspicious of why and how. But I did Soft Power , and they seemed to be ok with just me wanting to chill for a while.
What you're talking about doesn't sound correct. You apply for the Work Visa, and then you get 3 month Non-B visa, and once in Thailand apply for your work permit and then your extension of stay. At no point should your work permit hold you up from staying in Thailand.
The non-b Visa can be granted in 1 day if all your paperwork is in order.