EUROPEAN ROYALTY AND A THAI PRINCESS WERE GATHERING IN STOCKHOLM ON SUNDAY TO JOIN THOUSANDS OF SWEDES IN CELEBRATING KING CARL XVI GUSTAF'S 60TH BIRTHDAY. PRINCE ALBERT II OF MONACO, KING JUAN CARLOS OF SPAIN, QUEEN BEATRIX OF THE NETHERLANDS, PRINCESS SIRINDHORN OF THAILAND AND THE ROYAL FAMILIES FROM NEIGHBORING DENMARK AND NORWAY WERE AMONG THE HUNDREDS OF GUESTS SET TO ATTEND THE CELEBRATIONS, THE ASSOCIATED PRESS REPORTED. THE ROYAL FAMILY IS HIGHLY POPULAR AMONG SWEDES, AND SUPPORT FOR THE CONSTITUTIONAL MONARCHY SOARED TO 80 PERCENT LAST YEAR AFTER THE KING'S EFFORTS TO COMFORT THE NATION FOLLOWING THE SOUTH ASIAN TSUNAMI. HUNDREDS OF VACATIONING SWEDES WERE AMONG THE TENS OF THOUSANDS KILLED IN THE DECEMBER 2004 DISASTER. THE KING, WHO HAS NO POLITICAL POWER BUT IS SWEDEN'S HEAD OF STATE, MET HIS WIFE DURING THE 1972 OLYMPICS IN MUNICH,WHERE SHE WAS SERVING AS AN OFFICIAL HOSTESS AND INTERPRETER DURING THE GAMES. THEY WILL CELEBRATE THEIR 30TH WEDDING ANNIVERSARY LATER THIS YEAR. THE COUPLE HAS THREE CHILDREN: CROWN PRINCESS VICTORIA, PRINCESS MADELEINE AND PRINCE CARL PHILIP.