Recognising Thai currency quickly — denominations, colours, and the security features worth knowing.
20 THB (green), 50 THB (blue), 100 THB (red), 500 THB (purple), 1,000 THB (grey-brown) — colour-coded for quick recognition even before you can read the numerals.
1, 2, 5, and 10 THB coins in circulation; the 10 THB coin has a distinctive two-tone silver and gold appearance; 25 and 50 satang coins exist but are rarely used.
Every note and coin carries the King's portrait — treating currency disrespectfully (stepping on it, defacing it) is taken seriously; never place anything on top of currency at a table.
Higher denomination notes (500, 1000) have security threads and watermarks — genuine concern is low for tourists, but check large notes received in change at less formal settings.
Street vendors and small stalls often struggle to break 1,000 THB notes — carrying smaller denominations makes everyday transactions noticeably smoother.
Airport and city money changers will buy back unused baht before departure, though rates are generally better spending it down before flying out.