Hi SB1970,
1. Whether or not M'sian PPL is recognised by CAAS, you should check directly with CAAS. I wonder why do you need CAAS recognition because S'pore doesn't have airspace for GA. However, there is such thing called re-validation among ICAO signatories countries. Again, call CAAS to find out more details.
2. All AVMED Drs. are having almost similar qualification but the one that can sign the cert is the one who is licensed to do it by Civil Aviation Dept from respective country. If I 'm not mistaken, there are 2 S'porean doctors who are registered with M'sian DCA and both can sign medical cert. You may contact M'sian DCA personally to find out who are they or JFC should be able to help you in obtaining necessary documents.
Happy Flying
