I have just read about this proposed high speed train between China and Thailand. The Thai cabinet has approved the idea in principle but more negotiations are to come. This is a great idea and I hope it comes about in my lifetime. You can read more at http://www.thaivisa.com/forum/topic/396547-thailand-china-high-speed-rail-talks-get-cabinet-go-ahead/

I posted some info on my trip mid August on the new high speed trains in China in the Suggestions for destinations outside Thailand thread on the Gay Asia section. Best of all is the fact that the Thai train will be on dedicated track with a wider gauge.