But first, significant hurdles need to be overcome.
The two countries must decide on pressing fundamentals. These include the ownership, financing and operating models, as well as the project structure.
Then come decisions such as route alignment, number and location of stations along the way, form and location of checkpoint, and finally, location of depot and terminal stations.
Terminal stations should ideally be in the two city centres, as it would provide the best accessibility to travellers. But this may not be technically feasible or cost-effective, as both city centres are highly built up.
Already, Malaysia has identified Sungai Besi, a location 15km from the Petronas Twin Towers, as a site. That would be about the same distance that Jurong East (a location that Prime Minister Lee Hsien Loong seems to favour) is from Singapore's Central Business District.
If the two terminals are in Sungai Besi and Jurong East, a door-to-door commute by HSR is projected to be 190 minutes - still considerably faster than 255 minutes by air.
But these are details to be ironed out further down the line.
First and foremost, the two governments must be convinced that an HSR will be equally beneficial to both Singaporeans and Malaysians for generations to come. And they must have the political will to see the project through.
Indeed, besides financial capability, it is political will that is powering China's HSR programme. For cross-border projects, it was the political will of the Margaret Thatcher and Francois Mitterrand administrations that paved the way for the London-Paris HSR.
If Thatcher and Mitterrand could get the English and French to work together, despite the two countries' legacy of bitter rivalry, there is Hope yet for the Kuala Lumpur-Singapore HSR. It is a project the two sides have been mulling for 20 years now.
If it gets off the ground, it could potentially form the first leg of a South-east Asian network that links all the way up to China.
A look at the history of HSRs across the globe shows that worldwide, they do not seem to have a strong or clear proposition for many countries. Ever since the first line started running in Japan 50 years ago, only 15 other countries have followed suit with their own systems. In comparison, 126 metro systems were built in 50 countries over the same period.
But once overcome, the benefits are many.
ONE of the main impediments to HSR projects is cost. And because of the protracted nature of such projects, and their long gestation, cost overruns are also common.
For instance, the London-Paris line was projected to cost £1 billion when the two countries agreed to build it in 1986. By the time it was fully opened in 2007, the bill had escalated to £11 billion, according to a report by The Telegraph.
Land acquisition and environmental concerns (mainly noise pollution) are two other hurdles to HSR projects. Often, the latter cannot be overcome by going underground because of prohibitive cost.
But even if a line does go underground - as in the case of the proposed Tokyo-Nagoya maglev project, through a mountain range - it will still raise the ire of environmentalists.
The fringe benefits of an HSR project are not as apparent as those of a metro line, either. Property prices along the line seldom appreciate. In fact, they are liable to do the opposite. Reports by British realtors indicate that home prices near a new line from London to Manchester have already fallen by 40 per cent - even though the first trains are not expected to run till 2026.
Yet, whenever a HSR line is finally built, it proves its worth fairly quickly.
Faster, green commute
HSR provides a fast, smooth, safe and clean commute.
In a study of fatalities per billion passenger-km operated, the National Society of French Railways found HSR to be significantly safer than travel by air, road and conventional rail.
It is also the greenest. The study found that HSRs in Europe emit only 12g of CO2 per passenger, versus 30g for buses, 115g for cars and 153g for airlines. (France's HSR system supposedly emits only 2.2g of carbon per passenger - because electricity there is largely nuclear.)
Train tickets are also generally cheaper than airfares, and often, trains are faster door-to-door than planes.
The Chinese example
AND there is no better place to witness the rising popularity of HSR than in China, which has the largest HSR network at 10,000km - nearly half of the world's combined network.
And it is an impressive network, too.
When I took an HSR from Guangzhou to Wuhan in mid-2011, I was surprised by how luxurious it was. The seats and legroom were comparable to Business Class on a premium carrier. And even at 330kmh (this was just before the speed curbs following a fatal accident later in the year), it was as quiet and vibration-free as an A-380 plane.
In fact, I found it to be slightly more comfortable than Japan's Shinkansen, and far better than France's TGV.
I had commented to China Railway Corp officials how expansive the Guangzhou South train station was (bigger than some international airport terminals), and how sparsely occupied the trains were. But I was assured that both would be filled soon.
Indeed, HSR is hot in China today. So much so that airlines are feeling the heat.
According to a World Bank report in 2012, within three years of operation, China's HSR had adversely affected domestic airlines.
"Some short-distance air services have been completely withdrawn... routes from Zhengzhou to Xian and from Wuhan to Nanjing both survived only a few months after the opening of HSR," it read.
Air travel demand between Changsha and Guangzhou, a distance of about 600km, has fallen from about 90,000 passengers a month to 30,000.
Airline profits have also plunged, even in cases when actual passenger volume has increased. China Air for instance, posted a 32 per cent drop in earnings last year to 3.26 billion yuan (S$656 million) - despite a 0.4-point improvement in load factor to 80.8 per cent.
HSR ridership is still growing, with the state adding more trains and building new lines.
According to a forecast reported in The New York Times, China's HSR network will carry more passengers per annum than the 54 million carried by US domestic airliners by this year.
The only question mark hanging over China's HSR success story is profitability, and how long it will take to recoup the hundreds of billions in sunk cost.
In fact, this was one reason why the World Bank said it was "cautiously optimistic" about the future of HSR in China.
But the Chinese do not seem overly concerned. To the government, it is too early to talk about financial payback.
Instead, it is pushing ahead with expansion plans, both in terms of increasing the capacity of its current system to cater to growing demand, and expanding the network.
Changsha station for instance, will soon have 32 platforms - double today's 16. And it is all of four years old.
It is also said to be aiming to build another 15,000km of lines by 2020 - some to join up with lines in neighbouring countries such as Laos, Vietnam and Myanmar.
China to Singapore by rail?
LAST October , Chinese Premier Li Keqiang opened an exhibition in Bangkok with Thai Prime Minister Yingluck Shinawatra promoting a high-speed railway that would link China, Thailand and Singapore.
The proposed line would be able to carry passengers from Kunming in China to Singapore in less than 12 hours, reported China Central Television.
If this comes about, the Kuala Lumpur-Singapore HSR that PM Lee and his Malaysian counterpart, Datuk Seri Najib Razak, aim to build by 2020 may become the first leg of a South-east Asian network.
The story does not stop there. Professor Wang Mengshu, a rail expert at the Chinese Academy of Engineering, was quoted in 2010 as saying that China was exploring HSR links all the way to Europe.
If so, a traveller here could reach London by rail in under two days. That is, going by today's HSR capabilities.
China is working on much higher speeds. It is home to the world's only commercial magnetic-levitation (maglev) system. The 30km line takes passengers from downtown Shanghai to Pudong International Airport (30km) in seven minutes, reaching a top speed of 431kmh.
(I took a ride on it in 2005, and it was like flying at ground level.)
Japan has conducted test runs of its new maglev trains, reaching close to 500kmh. And China is said to be testing a "Vactrain" - a maglev in an enclosed vacuum tunnel - capable of 1,000kmh.
If these come about, one could commute from Singapore to London by train in 15-16 hours (including stops) - faster than a door-to-door commute by air (17-18 hours) today.
That is unlikely to happen in the near future. But 400-500kmh trains are conceivable, even without maglev technology.
It is therefore wise for builders of new lines to take this into consideration - to ensure that the tracks, power lines and signalling systems are capable of handling such speeds, or can be scaled up to do so.
But even before Singapore and Malaysia get to discuss such technical issues, they have to overcome the initial hump: Get over the barriers of high cost and environmental concerns, manage public expectations, and demonstrate clear political will to turn the Malaysia-Singapore HSR from rhetoric into reality.