I know my supervisor is good because I've been taught by him since first year in same faculty, and my other friend's also recommend him 

If you are outsider, your best bet is go through their research, and get review from student instead of lecturer ( as many lecture involve in office politics they might mengutuk each other)

For lecturer CV University Malaya you can refer this website http://umexpert.um.edu.my/cv_search_page.php

Please be noted that the quality of lecturer isn't proportional to number of publication, some lecturer who able to publish ridiculous amount of papers might involve in unethical/illegal activity include buy/steal other student's work, force other people to put his name in publication etc. I know a bangla lecturer in Engineering Depeartment of UM able to produce more than 30 papers within a year, that's average 1 papers per 10 days, so ridiculous 

For student review you'll have to go through FB or forum, its best that you could find postgrad student who under some lecturer as they should be able tot provide accurate review.