Compared with many popular holiday destinations Thailand is relatively safe. However, while the thai people are generally very tolerant when it comes to the behaviour of tourists it would pay to be aware of things that may cause offense or even unwittingly land you in hot water.
The following list contains a few pointers that might aid you in avoiding trouble or injury as well as some that may help you have a more pleasant stay.
Do Smile
Be respectful when bartering or doing business and smile. It is good manners to smile frequently in thai culture and it seems that you can never overdo it. Never lose your temper or, if you cannot help it, at least try not to show your anger as it is considered low-class behaviour and will gain you no respect at all. Being pompous and argumentative can often allow someone to get their own way in western society but the opposite can be expected in Thailand.
Do Not Show Disrespect for the Royal Family
The thai people adore their royal family and speaking ill or even flippantly about them can cause offense. In fact, its not seen as just bad manners, its also illegal and could lead to a jail sentence. In 2007 a Swiss man was sentenced to ten years in prison for defacing the King's picture in a fit of drunken pique (he could not buy alcohol as it was the King's birthday). He did eventually receive a pardon from the King himself. His Majesty King Bhumipol has done much for his country and it might be of interest to know that he is not in favour of this law.
Do Carry ID
Carry your passport or at least a copy of it at all times in case you are stopped by police or other government official. You are required by law to carry your passport but this is often not practical so many people carry a photocopy which is usually acceptable. Failing this, a photo driver's license will probably be sufficient for most situations where you need to identify yourself. It may save a fine and a visit to the station. But take care that you don't lose that Passport!
Do Wear Sensible Shoes
Its a good idea to wear sensible footwear as dangerous obstacles are common on thai footpaths. Back-less flip-flops may seem like a good idea but get caught in a rain-storm and they'll quickly become slippery and increase your chance of injury. Sandals are a much more practical alternative and can be bought very cheaply just about everywhere in Thailand.
Do Use Mosquito Repellent
Repellent containing a high concentration of "deet" is most effective, The most crucial times to use protection are in the evening (especially around sundown) and at all times if you are near standing water. Its arguable, but it does seem that mosquitos are particularly attracted to soft untanned skin so take particular care to spray some on until you've managed to tan slightly. Also take care to close your hotel room windows before sleeping and, if you spy one in your hotel room, don't sleep until you kill it or it WILL come and feed on you during the night. If mosqitoes are a regular problem in your room ask the staff to have it sprayed each day after cleaning.
Don't Touch a Thai Person's Head
The head is the most important or "highest" part of the body to a thai and casual touching of it even in a friendly manner can cause offense. The feet, however, are considered the "lowest" body parts and using them to do such things as point at someone or resting with them pointing in the direction of pictures of respected ones is considered very bad manners. You may be familiar with images of thai buddhists and monks sitting cross-legged in temples. This is so they avoid pointing their feet in the direction of images of Buddha or others.
Do Take Your Shoes Off
When entering a buddhist temple, someone's home and even some shops you should leave your shoes at the door. Its not needed in most shops but if you see a pile of shoes at the doorway then its best to take yours off before entering to avoid offense.
Do Wear a Crash Helmet
Wear a helmet if renting a motorbike or riding as a passenger on a taxi-bike. The police don't usually enforce the law with foreigners but there's a huge number of bike accidents so its probably an even better idea to wear one in Thailand than it is in your own country
Do Beware of Scams
As with many holiday destinations there are a host of scams to beware of. Basically, if someone in the street or a cab driver offers you a deal on things like gems or jewellery that appears to be too good to be true then beware.
Not quite a scam but very irritating can be the time-share operators' sales tactics. They pay usually pleasant young thai people to approach tourists with short "tourism surveys" which are really nothing better than a ruse to get your hotel name and room number. Before you know it, you'll be pestered with notifications that you have won a prize that you can only collect by turning up to one of their meetings. Some can be annoyingly persistent even if you tell them you are not interested in their "prize".
Do Not Do Drugs
Thailand has extreme penalties for drug offences including the death penalty for trafficking. Even use of a small amount of marijuana could land you in jail. Do not consider it during your time in Thailand. If you are ever offered anything while you are there do not be tempted to even joke about it as the person you are talking to could well be an undercover police officer.