Thailand is a wonderful country with much to do, well organized for tourism, and people are gentle and helpful. If you do run into any issues – one word of advice – it is a culture which does not tolerate confrontation especially from outsiders – settle everything low-key with a smile. In Thailand be prepared for serious heat and humidity if you are not accustomed to it.
The major temple complexes of Bangkok have much interesting architecture, utterly different from the western tradition.
Bangkok is worth at least a week, because it is just so rich in temple complexes and palaces, markets, outdoor stuff worth seeing (Chinatown day and night for example) – one of those inexhaustible cities unless you are living there.
In Bangkok you’ll find in a nice little restaurant called “Tongue Thai” on a side street a couple of blocks from the Mandarin Oriental Hotel. “Hot Lime Sauce Beef” – it’s very tasty!
While in Bangkok visit the Sukhothai Hotel – a very special place.
If you like old ruins, an easy day trip by train from Bangkok is to Ayutthaya (there are various ways it’s spelled in English etc.), an earlier important capital of Thailand (back vaguely around the 1600’s or so); it has endless old temples in various states of decay that are a lot of fun to wander about.
Ayutthaya is actually a very large area with a number of different complexes that are worth seeing, but you need transportation to get from one to the other. The best thing is to go in an organized bus tour that covers all the highlights there, including the country Royal Palace complex.
If you can get farther south to Phang Nga Bay (the location of James Bond Island), however, it’s incredibly nice, with cliff-edged small jungle islands you can visit by boat. The waters and beaches are cleaner also.
The interesting part of Chiang Mai is within the town walls and this is a rather small area that you can cover adequately for tourism over a couple of days. A must while there is an excursion to Doi Suthep. This is the key highlight of Chiang Mai.
Also a most important spot that you should not miss is the Sukhothai area. You can fly there with Bangkok Airways (good airline) from BKK. Once there, you spend two days, and hire a driver to take you to the complexes of Sukhothai Historic Park and Sisatchanalai Historic Park, where there are ancient ruins embedded in rich oriental landscapes. This is the historic heart of ancient Siam and has informed a certain amount of modern Thai architecture giving a modern idiom to these ancient styles.