Business or Work Visa only deemed valid till your work permit is valid . You have to leave with in 7 days of the work permit expires . But you might go out of country but next work visa will be very difficult as they find this and it's a voilation of Thai imm. rule
Their is no law which can force you to pay where as maximum police can file a Negligence driving case on you ,,( you should have a valid thai driving licence and you bike papers complete incl yearly tax). They can not do any thing much except threaten you
If company is officially closed so your visa and work permit get null and void , where as DBD and immegration data generally does not sync so you can ...at your risk