Pls give information about other proposed HSR other than KL-SG link.:cheers:
Map of SEA from google maps:
http://img109.imageshack.us/img109/7135/seaz.jpg
And map of Malaysia from google maps:
http://img171.imageshack.us/img171/9122/malaya.jpg
I can imagine the possible KL-Bangkok HSR line may be dangerous if Myanmar have a war with Thailand.

mahathir proposed it before, but in meter gauge.
HSR is possible for Singapore to Kunming, by:

KL - Bangkok, shared track
West Line: Bangkok - Yangon - Mandalay - Kunming
Central Line: Bangkok - Vientane - Luang Prabang - Kunming
East Line: Bangkok - Siem Reap - Phnom Penh - HCM - Hanoi - Kunming

Hanoi - Guangzhou HSR (either be Vietnamese operator or Chinese operator)
Hanoi - Nanning - Guangzhou - (Hong Kong?)

From Yangon to India via Bangladesh is ok.

The Guangzhou-HK HSR is planned but the university student in HK protest about this project. So I think not possible to build this link.
For the HSR to kunming, I got imagination the train might collapse with the animals:nuts:

i afraid about militants in northern laos, nothern thai and myanmar more than animals...

remember former golden triangle?
the lao side is not really safe.

I think just choose the narrowest place at the country and build there.