I heard from PCCW, the first commercial IPTV in the world under the brand name NOW Broadband TV, that they provide consulting services to True in Thailand for its IPTV.  I finally found that it's now on air in Thailand at this website 
http://www.truetv.in.th/th/In short, IPTV is digital TV signal sent to subscriber via broadband internet.  More info here. 
http://en.wikipedia.org/wiki/IptvI wonder whether anybody has any experience with this service.
In Hong Kong where NOW Broadband TV is on, the picture has a higher resolution than its competitor, CableTV Hong Kong which is equivalent to UBC in Thailand.  However, even though NOW Broadband TV is sent via internet at a speed of 3Mbps, I can notice the pixelation of the picture, 

 those you see on VCD, when the picture has lots of information, ie fast moving or lots of detail in the picture.  Nevertheless, the picture is nowhere near what UBC is in Bangkok, much better but you can still notice pixelation.
One good thing is that you can buy a service on an a la carte basis, ie if you only 

 1 channel, then just pay for that channel only!  You don't have to buy the whole package/bundle which you can pick and choose and don't have to pay for the channel you is less likely to watch.