I think it was 2 years ago that Koh Samui Airport was closed for 5 days in November due to the runway being flooded.

That's very unusual, but gives you an idea of how much rain you might expect.

However, you could very easily have an early / delayed monsoon. And even during monsoon you will see plenty of sun anyway. And the pay-off is that the hotels are very cheap.

Thanks for your help, I think we've decided against Koh Samui now, going to try Phuket instead I think or maybe somewhere more in the north.

Three years ago we had rain here on Samui for more than two months and it rained heavily almost every day. Last year we had almost no rain at all. Both these cases were extreme so you never know. Normally the monsoon ends a bit more late here than on the east-coast but on teh other hand the rest of the year use to be great.

I think Phuket is a great option for the November month, or Khao Lak.