A spokeswoman for Canterbury DHB confirmed that he remains in a critical condition today.
JJ suffered serious head injuries in the incident on State Highway One between the intersection of Curraghs Rd and Weedons Ross Rd at 3.55pm.
The driver of a dark silver/grey Mazda saloon was uninjured.
The car has been examined by the serious crash unit and the driver has been interviewed.
JJ's host parents today declined to comment.
Canterbury police investigations are continuing.
"Police are currently interviewing witnesses as part of this ongoing investigation," a spokeswoman said.
"The boy's family, who are understandably very upset, have been at their son's bedside since they arrived in New Zealand [last Wednesday] from Thailand."