As many ask- here are rainfall stats for TH for coming months
 

These are average rainfall stats per month ( inches ) as I know many ask this

Locations: Sep/Oct/Nov/Dec/Jan/Feb/Mar

Bangkok 1.6/9.1/2.3/0.4/0.4/1.1/1.2
Chiang Mai 9.9/5.2/1.7/0.6/0.3/0.2/0.6

Phuket 16.5/12.0/8.2/2.0/1.4/1.2/1.5
Samui 8.2/10.2/11.9/3.9/1,5/0.3/0.5
Hua Hin 3.2/7.9/8.0/0.3/0.2/0.6/0.6

I found those on the Worldclimate site. Naturaly they are averages but at least gives some idea.

ttt

for Lyndinla

ttt for our friend going from HKG to Thailand in January

ttt for Daisyho etc

As you cand see it's not too bad at all Samui december at 3.9, compares with about 2.0 for Phuket and 0.3 for HH'

so the odd shower and the odd rainy daytime but nothing to be unduly worried about, though higher, but you get the perspective looking at other months.

Thanks very much JamesA. I assume the situation in Krabi would be similar to that in Phuket?!

Yes, there may be more precise information but often some of the weather sites do not use 'common' names for places, so these cover general area, very roughly

Phuket = + Krabi / Phi Phi / Koh Lanta

Samui = + Koh tao / Koh Phangan / Surat Thani

Bangkok / Pattaya = + Jomtien / Rayong / Chonburi

Hua Hin = + Cha Am / Pranburi / Pak Nam Pran / Bang Saphan