Just a few things I think visitors might like to know before coming to Thailand...

1. The "Wai" is the prayer-like gesture which accompanies 'hello', 'goodbye', 'thank-you', 'sorry' etc...

   Hold your hands flat together at your chest, and bow your head so your nose touches your fingertips, ladies may also perform a very small curtsey-like bob, gentlemen may bow slightly, to show additional respect (perhaps to the man who retrieves and returns your stolen wallet, Khob Khun Maak Khrap!).

   In some ways the Wai is similar to a military salute, the junior person does it first and the senior person is obliged to return the gesture, 'junior' is generally by age, but also status; my maid who is much older than me always Wai's first. A notable exception is young children who are obliged to Wai their elders, a reciprocal Wai is not expected. Also, you should never "wai" someone of lower status (such as a waiter / waitress) although it seems like the polite thing to do, you'll only embarrass the person you're “wai"ing, and yourself.

2. Heads and Feet; The head is considered to be the most noble part of a person and should not be touched, even patting a small child on the head is highly disrespectful, although, northern Thai are more tolerant...

   Feet are the lowest part of the body, dirty and unpleasant, never step over someone, touch anyone or even point with your foot. Even an unintentional 'point' such as when you sit and cross your legs, could be offensive.

3. His Royal Majesty King Bhumibol Adulyadej Rama IX ( ภูมิพลอดุลยเดช ) is highly revered by Thai people. Considered to be 'semi divine' by many Thais.
   This reverence even extends to His Image, if a bank-note blows away, don't try to stop it by stepping on it, as it carries His Image, remember what I said about feet?...
   Keep His Royal Head the right-way-up in your wallet or purse, don't tear or even crumple a bank note. Never insult or criticise any member of the Royal family, Thailand's lèse majesté laws are harsh, you could earn yourself a free stay in "The Bangkok Hilton" if you do.

4. "Respectful Dress"; Thailand enjoys a tropical climate, so you may not think to bring long pants, this is a mistake, in some places, such as temples, certain government offices and some places of business, you will be expected to "dress respectfully" that means; no bare shoulders, bellies or legs. So bring at least 1 pair of long trousers or jeans and a lightweight long-sleeve cotton shirt... and thongs (NO! not the Am-English "thong"... I'm talking about footwear!).

5. Religion; The main religion in Thailand is Buddhism. Always show respect for monks, even give-up your seat on the bus for them, I've seen a very pregnant woman try to offer her seat, thankfully the monk smilingly refused. Women should take care to never touch a Monk, never hand anything directly to a Monk, instead you may have a male friend pass it for you, or place it on something and allow the Monk to take it.

6. Buddha; always show respect to any image of Buddha. Don't climb on any religious icons, no, not even to get a good picture, the 'no pointing with your feet' rule applies many times over. When you sit in a temple, on the floor, below the level of the monk who will be seated on a dias, cross your legs, sit sideways, fold your legs to the side... anything but point your feet at the statue of Buddha... or the monk.
   Thailand has laws and regulations regarding the removal of images of Buddha, as usual it difficult to learn the exact nature of these laws. And their application as you clear customs might just depend on how much the officer likes your jade Buddha souvenir.

7. Language; knowing the local language in Thailand is not the life-or-death issue that it can be in some countries, (France springs to mind... )
   English is taught in every Thai school and even my father-in-law remembers some...
   Thais are very helpful by nature, and even if you don't know the words "hong naam" a brief pantomime will usually be rewarded with directions to the nearest rest-room.
   However, Thais are also a very nationalistic and proud people, if you take the time and make the effort to learn some of their language you might earn extra 'brownie points' and respect.

8. Shoes; as in many Asian societies shoes are usually removed before entering a building. Of course there are exceptions... just look for a pile of shoes before you enter, if there are some, remove yours. It's a good idea to have footwear which you can slip in and out of easily.

9. Drugs; The Thai Government and police take a very dim view on illegal drugs and are sometimes rather 'draconian' in their methods of enforcement. For God's sake PLEASE don't try anything when you're here, death penalties apply! Nightclubs and other places of entertainment may be raided and patrons forced to present urine samples. A positive result will incur harsh penalties. Trust me; even if you don't receive the death penalty (sometimes carried-out 'on-the-spot' by police), the risk of spending half your life in "The Bangkok Hilton" is just not worth it.

10. Thailand is known as "The Land of Smiles". Thai people will often smile, or even giggle in the most unusual situations, such as narrowly avoiding a traffic accident. The reason is two-fold, first losing ones temper displays an enormous lack of self dicipline, something sub-human, and secondly it is not advisable to lose ones temper with a Thai person, a display of bad temper is extremely rude and will get you exactly no-where.
    The situation can easily escalate into a fully fledged brawl, and as you are probably much taller, heavier, stronger and possess a longer 'reach', Thai men feel no compunction about using weapons or attacking in groups. This has ruined the holidays of many a short tempered farang. The moral here is; Keep your head and you'll keep your head.

That's all I can think of for now... I'll add and edit as time goes by... Sawat dee khrap!

Please, read my article "Tips For Driving in Thailand" I know it reads like satire but the advice contained therein is serious! It applies to pedestrians too.