Tibet tour from Bangkok is no longer difficult anymore from October, 2013.
Chengdu, the capital city of Sichuan province, China, is not only famous as the home of panda but also known as the hub-city for tourists to travel to Tibet thanks for its convenient domestic transportation system linking Lhasa. It not only has a direct train to Lhasa each other day, but also more than 7 direct flights to Lhasa daily. So, if you find your way to Chengdu, which means you are at gate of Tibet too.
In the past, it was not easy for Thai people to travel to Tibet from Bangkok, because they have to fly to Beijing, Kunming or even Hong Kong and then continue to Chengdu and finally to Lhasa. From October 2013, China Eastern Airlines has launched non-stop flights between Bangkok and Chengdu; the flight operates every day, departing 20:20 and arriving in Chengdu at 23:55, the whole journey takes about 2.5 hours; air ticket is very cheap if you book early.