If you want to be able to service your ThinkPad here in Singapore Lenovo, you better check, double check and triple check with Lenovo Singapore to ensure that the overseas warranty is acknowledge here even thou it is a International warranty set.
So far, I got a friend with a ThinkPad which is US warranty started from 2012 (3 years) which he claim still able to service in Lenovo Singapore, so I cannot confirm if the above rumors are true or not as I have never own a overseas ThinkPad myself.