A little slim on information, you might want to state your passport nation, your age, the purpose of your visit and what type of visa you're considering.
They will want the bank statement showing the funds have been in there for 2 months plus they'll also want your bank book updated on the morning you apply for the extension.
You need to cancel your work permit and Visa extension. then you can exit the country there is no online visa for you unless you go to a Thai embassy You do have to fill in the TDAC form for arrival back in Thailand. Depending on your passport nation you may be eligible for a visa exempt entry stamp 60 days. Do not use the Poipet crossing.