Can Korean citizens extend their stay in Thailand for an additional 7 days after a 90-day visa exemption?

Hi, I need to ask you guys advice.

I am a Korean citizen and stayed in Thailand little more than 1-year using 90days visa exemption while traveling other Asian countries (Korea is one of the countries enlisted on Bilateral Agreement, which means I can stay in Thailand 90days without extension/tourist visa whenever I enter Thailand). I never did border run, always took a flight and stayed in other countries at least 5-7days. I have more than 5 thai in/out stamps on my passport.

I applied education a few weeks ago, I already submitted the form through my language school. My current 90 days visa exemption is going to expire on 14th, Jan. But my language school just said, due to the new year, the application has been delayed. I might be about to get my form back by 20th(or 22nd), Jan. So I need around 7 days more after my 90days visa exemption expires. Thai lady at school said there is 7 days visa extension for Bilateral Agreement countries, however, she wasn't sure. Do you know anything about 7 days visa extension for Bilateral Agreement countries' citizen after 90days visa exemption? Or should I need to go border run before 14th, Jan and is it still safe to try after 5 thai in/out stamps?

Thanks for reading and hope anyone has some advice!