There are 4 levels of teaching/coaching golf.  The first 3 are organised by the regional federations Golfvlaanderen and AFGolf in conjunction with the Royal PGA of Belgium.  Only the final level PGA Professional is organsied by the Royal PGA of Belgium.

As a (Belgian) amateur you need to have a handicap that is better than scratch (+0,5) before you can join the Royal PGA of Belgium.  You can also try to become a member of a third level Tour (ProGolfTour or AlpsTour).  

Once you join the professional ranks you need to change your status from amateur to professional.  You can do so by contacting the Royal Belgian Golf Federation.

All amateurs with a handicap <28.4 can play on the PGA Monday Tour.  You need to register free on the PGA Portal to have access to the calender.  Entry fee is €85 unless you join the PGA Club (€99 annual fee) which gives you a discount of €20 per event!.