Watched a tournament semi-final match today and a father was coaching his son during the rally. In between rallies, I understand. Almost all international players get coaching in between rallies. But is it legal during the rally? The father was instructing the son where to hit. For e.g. there's a gap down the forehand side and the father says "Hit it to the forehand" etc.
3.5.6.1 Coaching from off the court (Law 16.5.1) shall be prevented in any form from the moment when the players are ready to play and while the shuttle is in play. http://www.bwfbadminton.org/file_download.aspx?id=422658&tid=1 Recommendations to Technical Officials
16.5 Advice and leaving the court 16.5.1 Only when the shuttle is not in play (Law 15), shall a player be permitted to receive advice during a match. http://www.bwfbadminton.org/file_download.aspx?id=422701&tid=1 Laws of Badminton
As Fidget stated above, coaching is only allowed when the shuttle is not in play and during intervals. When the players are about ready to serve and receive, they must stop coaching. If heard by the umpire, the umpire may choose to play a let and inform the referee. The referee will stand by the coach and warn him if he/she sees them do it. If the coach continues, the referee has the ability to remove the coach from the match, or if persistent throughout the tournament, from the whole tournament itself.
OP, was this a young kid playing... probably not more than 12 yr old? If so, then makes sense for the dad to offer play advice, even though it really is officially prohibited.
Probably <12 years of age. Still does not make it ok though. In between points, yes that's fine but DURING the rally?