Cruises to Asia and the Far East are generally completed as extended voyages. Few cruise lines do them, and when they do, they are not repeatedly scheduled cruises. In fact, often the region is explored as a part of a World Cruise segment, and passengers not doing the entire World Cruise have to meet the ship in one of the Asian ports.
You can also take a standalone cruise to Asia. Many of them will begin in Bangkok and will visit a variety of Far East destinations such as Nha Trang, Phu My, Da Nang, Sanya, Xiamen, Singapore, Bangkok (Laem Chabang), Ko Samui, Sihanoukville.
The difficulty with taking a cruise of this type is the sheer diversity of the languages and cultures you will experience. Just about everything concerning the peoples and the cultures of these countries are more than likely to be different from anything you’ve ever experienced, and that’s what makes exploring this region amazing.