What are essential places/things to see/do in Thailand on holiday?

I'm going for a month's holiday, and will probably be based in Bangkok. Also, Which time of year is the best to go? I was thinking maybe June.

the less time you spend in Bangkok the better of a time youll have. when you arrive in Bangkok ...... check out the Grand Palace, maybe China Town, Jim Thompsons House ..... and get out of Dodge. Kanchanaburi, Cha Am, Hua Hin, and the Floating Market are all things to do relatively close to Bangkok and a lot more fun.

Actually, it is not rainy seao in June. The rainy seaon will start from mid of July.

In Bangkok, you can do and see anything that you would like to do or see...it will be very good experience and rememberable for you.

June would be the rainy season I think! You would definitely want to spend a few days at least on Phuket.

I think the best time to go would probably be February through April -- that tends to be the dryer season.