* Only 3 similar tenor bonds this yr in Asia have paid more (Adds sourcing on pricing details): HONG KONG, Oct 24 (Reuters) - HNA-affiliated Hainan Airlines - China’s fourth-largest carrier - has sold $100 million in two-year U.S. dollar bonds carrying a 12 percent coupon, in a sign of the financing strains felt by units of the indebted Chinese conglomerate. The deal comes as HNA Group is in the process of selling some $20 billion of assets, according to Reuters calculations and media reports, following a $50 billion acquisition spree.