Your employer should take care of renewal of your working visa if you have one, if not you're working illegally and should jog on out of Thailand before you get thrown in the Bangkok hilton
You leave on the 12 th Feb but you visa expires on the 4th of Feb?
AND YOU ARE ASKING OF YOU NEED TO GET AN EXSTENSION??? BALLON HEAD
No of course you don't, just slide 1000 baht into your passport when you're at immigration at the airport as you stamp out of Thailand and all will be find