The Foreign Office advice for British nationals was updated on 26 October 2011 as per below. Please note that transit through the international airport is still allowed.
This advice has been reviewed and reissued with
an amendment to the Travel Summary (update to advice and information on
floods). The overall level of the advice has changed. We now advise against all
but essential travel to the city of Bangkok and the 26 provinces in Thailand
affected by flooding. Our advice against all but essential travel to the
city of Bangkok does not include transit through Suvarnabhumi international
airport. Flights to destinations elsewhere in Thailand (eg the resorts of
Chiang Mai, Pattaya, Phuket, and Koh Samui) continue to operate normally.
http://www.fco.gov.uk/en/travel-and-living-abroad/travel-advice-by-country/asia-oceania/thailand
Our current advice to travellers remains the same. We will divert all tours away from Bangkok until 3 November 2011. After this date the situation will be re-assessed and a decision will be made on the tours commencing the weekend of 5-6 November 2011. Safety is our top priority and we will continue to monitor the situation closely.
Status of our tours to Thailand:
GTBC - Beachcomber - 30 October
GTLS - Laos & Cambodia - 2 November
GTLC - Highlights of Laos - 2 November
If you're booked onto one of these tours you will be contacted by our representative who will provide you with further information. All tours to depart after 3 November 2011 will run as scheduled.