It's not the next Google nor will it make you a millionaire like MySpace, but it is nonetheless a useful tool that will secure a good share of a niche market.
Originally, you intended to launch it in Singapore but after some market research and talking to industry insiders, you received very favourable response. Singapore is such a tiny market and you'd obviously like to make as much out of your idea as possible. Therefore you decide to launch it on an international scale, with a focus on US.
The problem is that, for it to be successful, you need people using it. Word needs to get out because the prime source of income would be subscribers. That's easy in Singapore because you're familiar with the industry and already have people interested.
But for a US launch, you're not confident of generating enough "buzz" with your meagre marketing budget nor do you have contacts over there to be the early adopter and spread the word for you.
Will you:
1a: Launch it Internationally, propogate it with primarily Singaporean users
The problem with this approach is that someone might find it great and "localize" the idea before your's is popular in that part of the world.
1b: Launch it Internationally and take out Adsense Ads
Cost increases and usefulness doubted. I'd probably get a better respond by searching for emails of industry professionals and mailing(spam

2: Launch a Singapore version, and put up a US site
Which is probably by far the best method. Local success ensured, foreign presence independant and a bonus. But global revenue is a more attractive idea!
3: Launch in Singapore ONLY, patent the concept and licence it out
Not a bad idea, but takes a long time, costs money and might fail because the concept is too "generic". Narrowing the scope of the patent is an option, but "competitors" can then always derive an alternate version that provides the primary functions.