Is there a regular bus service that goes from Nongbualamphu to BKK? Or better still one that goes from Na Klang?

I've asked a similar question before about a service from Udon but if we can get a bus from Na Klang/Nongbualamphu that'll be easier for us as it's closer.

I know I can fly from Udon but I'll be doing quite a bit of flying within a space of a few days so was considering the bus as an alternative.

Yes, definitely buses to and from N.B.L..If there is a bus station in N.K. ,then it is most likely that buses will pass through , on their way to Bkk..