Since the train is going to another country, there will be customs, security and immigration checks. As for checking in, even Air Asia has resorted to checking in from your PC. If you have luggages, the same challenges applies to trains. Will the train ask passengers to be at the waiting room early before boarding? I am pretty sure they would.
When you get off at Singapore, there will also be customs, security and immigration checks.
Lastly, its not really door to door as the article mentioned. You still need to travel to the station. And since they are not going to be stops in between, people in Kajang, Putrajaya, etc need to travel to Sentral train station (assuming its built there).
The London Paris high speed train partly works because you can travel througout Europe without going thru customs, immigrations (I am referring to EU citizens, non EU still need checks).
High speed trains crossing international borders suffer more or less the same process as air travel.
Anybody care to comment?
There are ways around it.
Passport control could be circumvented with bio-metric control for frequent travellers that uses the lines.
Baggage checks could be done quickly with right system in place to move people from the station to that country.
If implemented correctly, travel by rail is far more convenient than air travel.