Chapchai Nirat (born 5 June 1983) is a Thai professional golfer.
Chapchai is the son of a Thai national team golfer, and turned professional in 1998 as a fifteen-year-old.
He won for the first time as a pro at the 2004 Genting Masters in Malaysia.
He joined the Asian Tour in 2005, and had a second-place finish in his rookie season.
In 2007 he won the TCL Classic, which is co-sanctioned by the Asian Tour and the European Tour and the Hana Bank Vietnam Masters.
He was the third Thai to win a European Tour event.
In March 2009, Nirat shot 32-under-par over 72 holes to claim the SAIL Open, setting a new Asian Tour record for the best 72-hole score.