Here's some useful links to online stores in Thailand for consumer electronics.
First off home entertainment such as TVs, DVDs, Blu-Ray and Home Theatre.
Piyanas is Bangkok's leading high end hi-fi and home theatre center with several branches around the city. They sell Paradigm, Pioneer, Denon, Onkyo, Yamaha, HDi, Mordaunt Short, Mission, Boston Accoustics, Kef, Acoustic Energy (AE), Q Acoustics, Arcam, Audio Research, Audioquest, Bowers & Wilkins (B&W), Bose, Bryston, Cambridge Audio, Castle, C.E.C., DLS, Dynaudio, Energy, Focal, Harman/Kardon, Infinity, Jamo, JBL, Klipsch, Marantz, McIntosh, Monitor Kable, Monster Cable, Monitor Audio, Oppo, Pro-Ac, OS Screen, Panasonic, Polk Audio, Rega, Revolver, Rotel, Roth, Sonos, Sonus Faber and many more.
Hi-Fi Center Thailand has a decent selection of mid and high end hi-fi and home theatre including Denon, Kef, Accuphase, Elac, Krell, PSB, Velodyne and many more!
One of the cheapest in Bangkok for TVs; Plasma, LCD and LED HDTVs.
Power Buy have a large range of home electronics; TVs, DVD players, Blu-ray players, DVRs, fridges, washing machines, vacuum cleaners and some more unusual items like wine fridges as well as a fair selection of mid to high end hi-fi and home theatre equipment.
Online shopping for fashion, mobile phones, laptops, notebooks, digital cameras and other electronics.
Thai Second Hand; loads of second hand items including personal computers, mobile phones, laptops, notebooks, home electronics, automotive and many other classifieds.
Online shopping for digital cameras, film cameras, photographic accessories and more.