Hi my name is Yip and I am from Malaysia and would like to know some information about Ttrip to Tibet.

Hi, Yip.
you can start your trip from Xian.
I heard the TravelChinaGuide provides the tours to Tibet, but I am not sure whether they can arrange a trip based on your requirements. You may try to fill their blanks on https://www.travelchinaguide.com/tour/tailormade.htm. After that they will contact you as soon as possible to tell whether your tour can be made.