HK portion is indeed bigger. Not western country big but big enough for a proper meal.

Any of their meal would make me full without the need to order seconds.

In Malaysia? If you order chicken rice, any type of noodles, mee rebus or whatever, you definitely need to add on something, either a snack, a second meal, or even pastry or else you will go hungry before dinner time.

Also, in HK, they always comes with a drink or soup during lunch hour.