Regarding ATMs I would recommend that you use one which is on the premises of a large bank branch. Local banks include Bangkok Bank, Kasikorn, Krungsri (Bank of Ayudhya), SCB (Siam Commercial Bank), Khrung Thai, TMB (Thai Military). Any ATM in a bank branch will support CIRRUS. You might also consider bringing $100 bills.

Temperatures this week in Bangkok range from a low of 77 (25) to a high of 92 (33), with clear sunny skies, no rain and a relative humidity of 50%. There are two seasons here: 1.) Hot and Wet, 2) Hot and Dry! I'd recommend comfortable shoes/sneakers with socks (for visits to places where you need to remove your shoes), lightly colored cotton clothing: pants and a short-sleeved shirt or polo/golf shirt. Shorts, jeans, T-shirts and sandals are OK in most places. Carry an umbrella, if only to use when walking in the direct sunlight. If I know I'm going to be visiting a religious or Royal site I even wear a long sleeve dress shirt. I've never had to use any provided clothing but have seen conservatively dressed women (long pants, short-sleeved shirt) required to use a wrap-around sarong-like garment provided on site.

In general you should do everything possible to avoid conflict, and/or putting a Thai person in an uncomfortable position. If you do mess up address the situation there and then, with deference. Do not point your finger at a Thai person, do not touch their heads, do not point with your foot, or step over a person (who might be reclining). Give up your seat on public transport to a child. Personally I would recommend that you not return a wai, the traditional Thai greeting, rather lower your head slightly to acknowledge the wai. Never raise your voice. If you pass an older person, lower your head slightly. Do not discuss politics or the Royal family (with Thais, unless you are vary familiar with them), show respect for everyone and smile. If you're out and about at 8 AM and/or 6 PM, stop whatever you are doing and stand (still) for the playing of the national anthem. Same goes for a movie theatre or other event, stand for the tribute to the King. Having said that, Thais are quite used to foreigners and allows us maybe more leeway than they might allow another Thai. The culture of calm, quiet dignity is somewhat misunderstood. When they bust loose it usually ends badly.