Basically, when packing for three weeks in Malaysia it is generally the same as Australia. I spent a lot of time researching and looking up what to wear while staying in Malaysia. I was a little anxious as I have changed clothing sizes in the last couple of years and had to buy new clothes for this trip. By going by what I found from research, I packed three quarter shirts/shorts, long pants/skirt and professional modest clothing in general. I really felt I did pack to much in the end. The backpack was still well under weight at 18 kg’s, however, I really could have ditched a lot of clothes which I did not end up wearing and taken a smaller bag as I prefer traveling light. Also there was a laundry service in the hotel which I used frequently.
From experience when staying there for the three weeks, people were basically wearing the same as what is worn in Australia. Including the appropriate attire you would wear for various types of tours, events, weather or religious activities you are attending.
I found from this experience, that it is more about being respectful to the culture, respectful to the people (the Malaysians) in a different country as it is their home. Malaysians in my experience in the three weeks were very hospitable, friendly, showed great passion for providing delicious fresh food and had exceptional customer service everywhere you would go. I was in a well established area of Malaysia, however, staying at a 4 star hotel with a tour group if that may have contributed to that, I am not sure.