There are many web sites which give guidelines to follow regarding Thai culture. e.g.
http://www.woodlands-junior.kent.sch.uk/Thaicult.html

There are seven broad hill tribe groups in the area we visit: Karen, Lahu, Hmong, Lisu, Akha and Mien. However, within these categories, there are sub-categories and clans that further divide the groups.
Each hill tribe has its own customs, language, dress and spiritual beliefs.
Avoid confrontations - Best advice is to stay cool, be cool, after all your on your holidays, smile a lot, and be on your best behavior. and above all, show respect for the Thai Royal family, monks and religious temples and shrines.
The hill tribes are most distinctly recognised for their colourful and unique costume, which they continue to wear daily.
Our own observations are - First and foremost, Thai culture is based on respect. respect for the Thai King and royal family, respect for Buddhist monks and Buddhism, then respect for your elders and respect for everyone else around you.
The people are courteous, there is a great deal of tolerance and people smile all the time. local people will take an interest in you and engage with you in conversation.
We are often offered food and something to drink in the remote villages we visit.

....and remember if we are invited into someones home, remove your boots.
The Thai culture is quite different from anything in the west, it can sometimes be a frustrating place for Westerners but if the visitor first of all understands its not like home and can keep an open heart and mind, they will come away with a very rewarding experience.