Non b visa extension under "considiration"

Hello,

I have non-b visa which last till 25.02, HR of my company brought me to Immigration in Bangkok 24.02 to get 1yr extension, that day I got new stamp in passport that my extension is "under considiration till 17th of March", as I know my HR came back 17th of March to Immigration (its Division 1 in Bangkok) and were told that stamp will be next day in passport. Since then they are comming back everyday and get information to come back "next day". In diffent time I could wait but I have plane booked for tomorrow to get to Europe and I cant change date. As I was told we can take my passport from immigration but without extension stamp, and I will have to pay for my overstay. 

DId you have situation like this before? If I will have to pay for overstay how I should calculate this - since original visa date (25.02), or since "considiration" date (17.03)?