If you get caught, they can void your visa. (seen a guy using a edited tm30 to apply for visa extension recently. the imm lady just told him to wait while she check the system. Told him to go get a real copy and shoo him off. Surprise they did not get the police to nab him.)
Best nightlife is in bangkok, RCA, Ratchada's soapy massage, patpong, nana etc. Shopping is also the best in Bangkok, icon siam, siam paragon, central world, otop market etc. Except there is a nice beach in Phuket.
You can do your own 30 days extension. Just bring tm30, a passport size photo, passport and copies, 1900b cash. You can take a bus to bangkok, than another bus to Cam (might get deny when you want to stamp back on the same day, and they might ask you to stay a night.) or you can get another bus to lao from the same bus station (mo chit) (nong khai. and take a tuk tuk to immigration, after stamp out, take a 30b bus to lao immigration. Nakornchai Air is a nice bus service.