Asia - BKK-SIN-KUL trip in January?

Planed this trip in January, trying to cover these 3 cities in no particular order and visit all the main attractions. The questions are:
How is the weather this time of year? Does it rain much? How much time would you suggest in each city? Are there any "must see" side trips?
Thanks for all your input :)

Start with...

http://wikitravel.org/en/Bangkok
http://wikitravel.org/en/Singapore
http://wikitravel.org/en/Kuala_Lumpur

...and then come back when you have an actual question.

Read it all, have planned a bunch but I am looking for your input, that's why people post here, right? to get personal opinions of other travelers.
Now the questions are:
How is the weather this time of year? Does it rain much? How much time would you suggest in each city? Are there any "must see" side trips?
Thanks you for all your input ^

We're happy to give personal opinions, but you've got to give us something to work with. How much time do you have? What are your interests?

And as far as weather goes:
http://www.bbc.co.uk/weather/world/city_guides/results.shtml?tt=TT002780

How is the weather this time of year?

Beautiful in BKK. The west coast of Malaysia can get rain any time, however this is the better time to be moving up and down the coast as the east coast of Malaysia in the monsoonal pattern. I'm not familiar with SIN this time of year, though my guess is rain will be the expectation.

This is something you can easily verify using weather.com or another reputable site.... reputable with the knowledge that weather is inherintly variable these days in SE Asia.

This is THE best time to go to Thailand. Dry and not that hot.

I like Singapore but do find it expensive, one or two days for me is enough. Same for KL as far as time goes but visiting the beach areas of Malaysia would be nice.

I personally love Thailand and if I have pure vacation time I concentrate it in Thailand. Bangkok can be explored for days and then there is Chaing Mai and Phuket, too many choices really.

KL / SIN are both big cities and unless you are there for the shopping 3 or 4 days will be plenty to see the sites, as this is the tropics it rains most afternoons between 4 and 6 for an hour or so but usually ready for a beer then anyway :)