Do you need to be MAS licensee in order to do portfolio management ? Under what circumstances will you not find the entity in MAS directory ? ?

Plenty.

Even Conservation Capital, which most of the community knows pretty well by now for buying and selling half-done Endowment plans, is not MAS regulated.

There is a large group of business entities that do portfolio management which are BOTH not MAS-licensed AND not on the MAS Investor list. So I can't really specify what kind of circumstances, since there's many reasons for them not and being on the MAS Investor Alert list.