Every country has a different flag day. In the USA, Flag day is on June 14.
In Thailand, Flag day is on September 28. Flag day in Thai is เธงเธฑเธเธเธฃเธฐเธฃเธฒเธเธเธฒเธเธเธเธเธฒเธเธดเนเธเธข (wan prรกย rรขatย taanย tong-chรขat-tai).
เธงเธฑเธ (wan) means day.
เธเธฃเธฐเธฃเธฒเธเธเธฒเธ (prรกย rรขatย taan) is a royal word meaning to give the flag.
เธเธเธเธฒเธเธดเนเธเธข (tong-chรขat-tai) means Thai national flag.
เธเธ (tong) by itself is flag.
เธเธฒเธเธดเนเธเธข (chรขat-tai) means Thai nation.
Flag day became official on September 28, 1917, as its the day the current design became official by Royal Decree from King Rama VI.
For Flag day (in general) you can just say เธงเธฑเธเธเธ (wan tong).

Information about the Thai Flag
The Thai flag ๐น๐ญ has 5 horizontal stripes. The top and bottom stripes are colored red, the inner top and bottom stripes are colored white, and the middle stripe is blue.
Did you know, the flag used to have an Elephant ๐ in it? The elephant was removed from the flag due to the king noticing the difficulty people had ordering the flag from other countries and also the flag was sometimes positioned upside (with the elephant upside down).
To learn more about the history of the Thai flag, please visit our article.

Flag / Flag day vocabulary
- Flag
เธเธ
tong - Stripes
- Stripes
เนเธชเนเธเนเธเธ
sรขyn tร ep - Colors
เธชเธต
sฤe - Red
เธชเธตเนเธเธ
sฤe daeng - White
เธชเธตเธเธฒเธง
sฤe kฤao - Blue
เธชเธตเธเนเธณเนเธเธดเธ
sฤe nรกam ngern - Pole
เนเธชเธฒ
sฤo - Waving
เธชเธฐเธเธฑเธ
sร -bร t - Raise the flag (by pulling the string)
เธเธฑเธเธเธ
chรกk tong