We used to have a local shortcode for Singapore. Unfortunately, the paid customer base that was supporting the operation and expense of that number was not at the level necessary to maintain it, and we discontinued service almost a year ago.
The number did "hang around" for awhile due to a mistake on the providers part, where it actually remained working after we had ended our contract. Since then we have changed all of our Singaporean users back to the Australian number for SMS voting, as the shortcode is no longer reliable, and we're not paying to support it.
Shortcodes are very expensive to setup and maintain. The countries where we currently support local shortcodes are the US and Canada. This is due to the large user base of premium(paid) subscribers. We may revisit a local Singaporean shortcode in the future, but we would need to have a similar user-base to support it.
For now I would recommend web or twitter voting as an alternative to sending international SMS messages.