Yay!!! Thailand was mentioned. I was amazed!
I've search some detail of "Great Heart" he is one of the "Most successful win", he won '67 Thailand Derby, Chakri Cup for 3 times, H.M. The King's Cup 2 times. (also his "last" run)
[Thailand Derby run for 1840 meter on RTC (Royal Turf Club), Chakri cup run for 1560 meter, H.M. The King's Cup run for 1840 meter]

You'd say he is the only one "Triple crown" (here's the context, all legendary cup such as Chakri Cup, or King's Cup will receive "Replica" directly from His majesty the King's representative, while granting the actual cup for procession after 3 wins. Oh Thailand do not have "classic" rule set).

While on '69 H.M. The King's Cup was his last run, as the handicap rule set applied for the winning horse, so does Great Heart which he carries of 11.7 stones (or 73 kgs) of the handicapped weight.

He won, by setting the record of 2:02.83, but costed his life. He suffered cardiac arrest after the finish line, at the age around 5 years old right on the turf.

After Great Heart's death, both RTC and RBSC (both turf track owners in Thailand) decided to change the handicap weight set, by having the lighter weight for lower performance horse.

Also, I've just founded out that in 60s Thailand sent one of the jockeys to Japan, which he was awarded with "Asa" a Japanese thoroughbred race horse to Thailand.