Temples and pagodas
Dress modestly: cover shoulders and knees. Remove shoes before entering temple interiors and some pagoda halls; remove hats too.
Walk clockwise around stupas and altars. Ask before photographing monks or worshippers. Donations are voluntary.
Daily life
Remove shoes when entering someone's home, and many homestays. The head is the most sacred part of the body: don't touch anyone's head, including children's.
Bargaining is expected in markets but not in restaurants or malls; keep it friendly and smile. Losing your temper loses the negotiation.
Chopstick rules: don't stick them upright in rice (it resembles funeral incense), don't point with them, and use the communal serving spoons where provided.
Sensitive topics
The war is called the American War here, and it is recent history: be respectful at war sites and museums. Politics is not a casual conversation topic.

