I can't speak to Singapore or Seoul. But in BKK prices are typically the same or maybe even a little higher than what I would see here in the USA. You may be better off buying one at home depending on what your prices are like there comparatively.

There are a couple of big retailers for electronics in BKK. Powerbuy is probably the biggest. They have a nice branch at Central World. Or you can go to Siam Paragon and shop on the technology floor. Lots and lots of electronics shops there. Or there is always the giant maze that is Panthip Plaza. Tons and tons of camera and electronics shops there as well. But I think the prices are all pretty much the same everywhere.