Converting the Singapore driving license to the international license was easier and faster than I expected. I managed to convert and get an equivalent international driving license at one of the Automobile Association of Singapore (AAS) branches.
They call it the international driving permit (IDP) on their website.
There are two ways to apply. One's through online, and the other is over the counter.
For online application, the website mentions a processing time around 5 days and delivery time of a few more days.
For over the counter, if you head down to the AAS branches, you can get yours within 15-30 minutes depending on the queue if there is any. Just visit the AAS website to find the addresses of those branches. Remember to bring your driving license there.
When I was there at the Ang Mo Kio branch, I was given an iPad to fill up my particulars. Then I had my photo taken with the iPad. And a few minutes later, the license was ready. All for SGD $20, not including admin charges.
I've a Class 3 driving license in Singapore. On the IDP, the equivalent is a Class B under the 1949 convertion, which is for vehicles not exceeding 8 passengers and vehicle weight under 3500kg.
The IDP is valid for one year from the registration date.
A lot of countries accept the IDP and you can check out the whole list on Wikipedia.
Strangely, I was told over the counter that Vietnam is not in the list, at least on my paper license, but on the Wikipedia page Vietnam is listed as one of the countries that will honour the license. Other countries near Asia that are not included would be South Korea, China and Mongolia.