 During the Second World War, he commanded the Phayap Army's 3rd Division before being made military governor of the Shan States, which Thailand had occupied during the Burma Campaign.Phin was the son of a Chinese physician, Kai () who migrated to Siam from Chaoshan, as was the father of his wife, Lim Hong (), who was also an immigrant from Shantou.His son, Chatichai Choonhavan, became Prime Minister of Thailand.