When Thai billionaire Shanin Chearavanont purchased a stake in China's No.2 insurer worth US$9.4 billion, it needed a financial backer. This mystery financial backer was UBS, who offered a complex financial package known only to very few people.

This was confirmed by individuals knowledgeable of the matter who spoke on condition of anonymity to Reuters. This backing for the largest foreign stock purchase ever done in China would explain how the richest person in Thailand with his conglomerate would be able to raise US$7.4 billion for the final payment at the 11th hour.

The purchase of 15.6% stake in Ping An Insurance Group Co of China by CP Group from HSBC was not disclosed and remained unreported until now. The central piece of the package was a five year US$5.5 billion loan according to Thomson Reuters information.

This was also another milestone for UBS, who is expecting a windfall of US$100 million for the package. This alone makes it one of the largest earned fees by a bank for a transaction in Asia.

Both UBS and CP Group declined to comment on the matter.