Horror stories!
I think you can extend for a further 2 weeks whilst in Thailand. It costs around 1900 baht and a visit to the nearest Thai immigration office. Otherwise just do a border run, mainly Cambodia, to get another 30 day extension. You leave at 6:00am and are back by about 2:00pm and the cost including liunch is around 2,300 baht. quote]
Or if you want to be really tight- catch the 6am train from Huamphlong station in Bangkok to the Cambodian border for 30 baht. Then just catch the afternoon train or one of the 20 or 30 different bus providers to get back to BKK.
That's what backpacking does to you!