The ESC is called Speed E-pro and it looks like this:
This ESC is made by a local RC company (HK based) but its not widely sold. This ESC is for sensored brushless only, so if I take out the sensor wire, the ESC will not work at all.
I suspect the problem is the ESC itself, since I have tried other motors on different ESC w/o problems. Maybe the sensor board on ESC or maybe a blown FET...
BTW: Thanks for all the suggestions so far.