Originally Posted by HK_Katherine:
Crap advice which depends on the company. We prefer internal candidates by a big margin.
The OP needs to figure out if it's the company which is paying below market or if he just has the wrong expectations - 25k is not bad salary in HK for a job with many possible applicants, like software would be.
Re the visa - you have to reapply for a new visa with your new firm. Somewhat more likely to be approved given you have already had one, but not certain. Many people will tell you that you can "transfer" your visa - that was never strictly true in the past and is even less so now.