I second the recommendation to go to MBK Center in Bangkok for mobile phones -- amazing !!
Also, I have been very pleasantly suprised at how competitive Bangkok has become in electronics pricing -- at Pantip Plaza in the last year I have purchased a high end laptop (same price as in USA and 20% less than cheapest available in Singapore ), two digital Sony cameras (roughly same as US, and line-ball with Singapore), and a 1Gb Sony memory stick (10% more than USA but 30% less than cheapest in Singapore) ..as a sampling
Hong Kong I used to shop all the time..no more
Tokyo .. forget it unless you want stuff not available outside Japan
Enjoy and take a few massages !!!