In KL there's an 'ALOFT' hotel which is new and pretty decent that's also connected to KL Sentral - probably cheaper than the Meridien / Hilton and just as convenient ( it's attached to the 'NU Sentral' Mall on the South Side of the station.. the other two are on the North Side )
But really I'd have to say as above .. decide where you're going first and then work it out ... not sure having a 'base' to leave stuff on a 3-4 week trip makes that much sense ? .. How much do you need to bring ?.. laundry is pretty cheap in SE Asia ... and if you want to mix SE Asia with NE Asia that's quite a big distance in between !