Captain Swing wrote:Is there a definitive answer?
Technically the definitive answer is Thai law says the actual passport must be on the foreigner's person at all times.
Realistically, hardly anyone carries around their actual passport unless they are going to use it for something. It is wise to at least have a copy of the main page and current visa.
If it helps, I don't recall any western farang who has ever been arrested or fined for carrying only a copy unless arrested in connection with some other crime.