I was also going to come on to say the air-conditioning will be cold! I actually usually need a light blazer inside the meeting rooms, which I then carry between.
Light, airy dresses, such as sleeveless wrap dresses are usually my go too, with ballet pumps. I also don't take a raincoat, just a brolly. When it rains it pours, so you wouldn't want to be out in it anyway! A brolly will get you to the nearest shelter. It's what everyone else seems to do and some of the buildings / metro stations are linked by covered walkways anyway.
I love KL, you'll have a great time!
Also, expect the banquets to be long quite formal affairs (although business wear not necessarily formal clothing): the ones I have been to have had lots of thank you speeches and a lot of respect given to any dignitary. We had a local mayor type person at one and we had to stand for him to enter and leave the room.
The food is absolutely delicious, if you can get your hands on laksa then do (the ones in the UK pale in comparison mainly because of herbs and spices that aren't easily available here). And nasi goreng (watch for the sambal being super spicey)...
Sorry, I know you asked about clothes and I massively digressed... 