Many Thai people will be wearing black or white, but this isn't mandatory. Tourists aren't expected to dress in the same way as Thai people, but showing respect will be appreciated by locals.

Yes, you can wear black in Thailand, and in 2026, it is actually a very common color for both locals and tourists in urban centers like Bangkok. However, the cultural context of black clothing in Thailand is significant. Traditionally, black is associated with mourning and funerals. While you won't be scolded for wearing a black t-shirt while sightseeing, you should be aware of "reading the room." For example, if the country is in an official period of mourning for a member of the Royal Family, locals will almost exclusively wear black or white as a sign of respect, and tourists are encouraged to follow suit or wear subdued colors. On the other hand, during the Thai New Year (Songkran) or other joyous festivals, wearing black might be seen as slightly out of place amidst the sea of bright, floral "Songkran shirts." As a rule of thumb, black is perfectly acceptable for daily wear, provided you follow standard modesty rules (covering shoulders and knees) when visiting temples.