I'm from Vivahomes Realty (USJ branch). Vivahomes has about 10 branches in Klang Valley. Before this, I worked for iProperty so I had the knowledge of which property agencies were the biggest, financially solid and had good SOP because they are one of iProperty's biggest agency clients. Vivahomes has all the structure and progression in place , not to mention 2x monthly commission payout. In my branch, majority of us do both subsale property mkt and rentals.
Other than a reputable agency, you should have a discussion with the team leaders as they are the ones who will guide you and help you learn the ins and outs of being a real estate negotiator (REN). It's just like working as an employee in a company, although the company itself maybe reputable and has a good platform, ultimately the person who supports/guides you will be your direct team lead. I suggest that you have a talk with a few team leaders if you are interested to join as a REN.
Other major real estate agencies in Malaysia are IQI, Hartamas, etc. Feel free to contact me for further information, 0126917370