GPS receivers, verboten in certain countries?

I'm thinking about taking a GPS receiver on my next trip to Singapore,
Thailand and Taiwan.
I have to fly through Seoul and wish to keep the thing in my carry-on.
Are the authorities likely to get a bit starchy? I figure I'll take
the batterys out of the unit but still...?
I may be out beyond Kanchanaburi towords Nam Tok. Do the local
constabulary get uptight about GPS units?
No wisecracks about navigational skills please, unless they're
particularly witty. ;-)