The thai youth of today are taking this langauge to places it has NEVER been in the history of the language! They are purposely misspelling words, adding tone marks to words which can't use that mark, and changing the definitions of words as they see fit.
This has caused much consternation and vexation by the "powerz-that-be" (ไดโนเสาร์ เต่าล้านปี - dinosaur, million year old turtles) who are alledgely entrusted with preserving the language.
Just so you know ANY language needs to be looked at like a living entity. It must evolve, progress and change based on the demands of the people using the language. The minute it becomes stangnant, doesn't develop it starts dying.. I for one applaud the thai youth of today for taking this langauge which was stangnant for a LONG time into a phase where it is developing at a rate almost too fast to keep up with.
BACK ON TOPIC:
The word เงิบ in the slang of today means หน้าแตก, which translates directly as "broken face", or ขายหน้า which translates directly as "sell face". In reality both terms mean "to lose face". Given the fact that thais are consumed by, saving face, giving face, gaining face and NOT losing face, it is no wonder this term sprang up. It has went from the word หงายเงิบ to just the word เงิบ and can be said when someone does something stupid..
This video by Adam Bradshaw explains it quite well!
หงายเงิบ starts around 1:58, but the whole video is worth watching!
Sorry I tried to paste the youtube video into the post but it wouldn't display. I just linked the URL instead...