For a business setting, women usually wear a knee length or below skirt suit. Whereas a businessman may prefer lightweight suits and cotton shirts.

For casual wear, trousers/Capri pants and T-shirts are acceptable but not swimming T-shirts and shorts (a light weight long pants are better than shorts). If you are wearing a thin long-sleeved shirt, you should wear a sleeveless T-shirt under that. The wrapped Thai skirts are decent enough and cool for hot weather. It is important to dress decently so that the locals and/or families are not hesitant to approach you.

For visiting a royal place, long pants, a plain shirt and sandals are acceptable.

For visiting a Buddhist temple, a decent dress (shirts with sleeves) with easily removable shoes are suitable because you cannot wear shoes in the temple. Socks are not appreciated inside the temple.

Women should not go topless on the beach and are often advised to wear a T-shirt over their swimming gear, although you will find that many women ignore this at the popular beach resorts. Off the beach, it is improper and actually illegal for both men and women to walk around topless.

Adventure travelers may feel comfortable in shorts and pullover cotton shirts. This is acceptable.

During the rainy season, lightweight cotton clothing will be better as they dry faster. Sandals will not get waterlogged like leather or athletic shoes, but they may be frowned upon in some venues.

If you are travelling to mountainous areas such as in the North, a long-sleeved shirt or light jacket is often advised for night time outdoors.

For adults, a pullover shirt with a collar makes a much better impression than a T-shirt.

Grooming is important to the Thais. They tend to shower several times a day as the heat and humidity in Thailand makes people sweat a lot. So, plan on regular Thai-style bathing!