I am considering travelling to Malaysia /(Penang-Langwaki) or Thailand/ Phuketin October but believe that it could be the rainy season please let me know if that is correct and also any suggestions of places to stay

You can check on the historical weather patterns by looking at www.weatherbase.com This website gives you month by month information on rainfall, high and low temps, etc.

Are you just looking for a beach, or do you want some cultutal expereinces as well? (For instance, Penang's beaches aren't very good, but Georgetown is fascinating and the hawker food is wonderful!)

You'll have to give us a per night price range in order for us to help on suggestions for places to stay. And tell us what is important to you in where you stay.

Last, let us know where you are coming from and whether this is part of a longer trip to SE Asia.

I intend coming from Ireland 2 week trip mainly relaxation budget would be fairly ok, looking for good quality hotels (3/4/5/ Star )in any of the resorts but it is mainly the weather that would be causing me some concern, I do not want to be looking out of my hotel room for the 2 weeks

Have been to Koh Samui & Bangkok previously and really enjoyed it but I never visit the same place twice as the world is to small for that

Which month do you plan on going? People can't help you otherwise.

I THINK you are saying October clonard. In which case you are not looking at the best time for Phuket,.... September---October being the wettest time of the year and the same goes for Penang/Langkawi.

Sorry, didn't see October. What about the east coast of Malaysia instead?

Open to suggestions re East Coast of Malaysia or other alternatives

October is always difficult as the seasons change, September I would say Gulf area Thailand, November then perhaps Phuket/Langkawi area, it's a tight call weatherwise October.
If you have done Bangkok and Koh Samui already and want somewhere different tell us if shopping/restaurants/entertainment are important or not, it's time I topped the rainfall stats for October again, take a look at that to get a perspective.

Weather in Bali is perfect in October.