Wow, Oct is one of the few months when normally ALL areas are in wet seasib. Samui-Phangan-Tao's wet season tends to kick off in Oct so if this year sees a late start that might be okay. Elsewhere Ko Samet tends to be one of the driest islands - and my experience of the Andaman in wet season is that usually there is plenty of sunshine for a good beach holiday.
I'm a weather nerd - this is my usual spiel for Oct (may be some repetition).
October is usually one of the wettest months in all areas. But we still get plenty of posts saying people had a good holiday with the usual daily mixture of one or a few showers/storms and sunshine/scattered cloud, some days with no rain. This has been the pattern in all my wet season visits (one of these went into early Oct.)
Prolonged wet periods are not too common in Thailand but I have to say in all the years I've been following the wet season (I'm a weather nerd) the most complaints of this have come from the Samui area islands in Oct, Nov and early Dec. But things are variable - I've only visited this area once during THAT period, in Nov 97, and I got good weather.
September in this area tends to be the end of its drier mid-year period, so if your visit is EARLY Oct, you may have a better chance of less rain than later.
Seems to me the really bad years tend to be about one in 4-5, but not necessarily every 4th-5th year.
Statistically the driest island in an average Oct has been Ko Samet (216mm and 15 days with SOME sort of rain - on some days this could be a short shower at night). Most of Samet's beaches face east and are sheltered from the prevailing wet season winds which on the days when they get stronger can cause rough seas and blow a lot of flotsam and jetsam onto exposed beaches.
The wettest are the Ranong
Islands of little Ko Chang
and Ko Phayam (414mm-24). Samui has averaged 304-20.
Anecdotally and statistically wet season tends to end earlier in the eastern Gulf than other island areas. So if you are going LATE Oct you may find Big Ko Chang and its neighbours drier than most except Samet.
If you look at the stats for the north in the second link below you will find rainfall totals seem to drop earlier there too. The central area around Bangkok seems less wet also.
#2 tezza has been a member since 13/4/2006. Posts: 1,338