Starhub (Singapore SIM) $15; 2.4GB for Use in US, UK, HK, Aus, Singapore, Thailand, Taiwan, Indonesia, Malaysia

Firstly, full 100% credit to StrayfireX from Ozbargain for this post.
I have done basically a copy and paste of the description and removed some of the points/text that were more relevant to Australia.

This one is valuable because this is a Singaporean SIM card that offers roaming rates identical to the normal Singaporean data rate which is pretty cheap across several countries.

• 1.2GB/30 days $10
• 2.4GB/30 days $15
• 3.6GB/30 days $20

This $15 SIM includes $18 of credit with the SIM, which means you can instantly activate it with the 2.4GB plan or somehow recharge $2 for the $20/3.6GB plan.

You can use this data in:

• Singapore
• Australia
• Hong Kong
• Indonesia
• Malaysia
• Taiwan
• Thailand
• UK
• USA

I believe the best value for this SIM lies in:

• Wanting to do a SE Asia trip across several countries
• Getting cheap data for the USA where comparable data is more expensive. As you can see $20 USD for 2GB, USA only, not including state tax or the price of the SIM which can be as high as $20 USD if you go to a T-Mobile store. $20 + $20 + 8% tax = $43.2 USD = $58.42 AUD.
• A real month for expiry
• 100GB of 3G data for use in Singapore in the first 3 days (dunno what you'd use it for tbh)
• Being machine washable.

Other stuff:

• Roaming partners and additional information available in the clicky.
• For T-Mobile using travelers, the other option is to use the Tourist plan which is $30 SIM included for 2GB of data and unlimited domestic/int'l and 1000 min domestic talk texts for 3 weeks (21 days) so that $30 USD + state tax ~ $43.82 AUD
• Probably not possible to combine with the Changi Airport $40 voucher given that it excludes the retailers that sell the SIM, but hey you might get lucky and find it somewhere else? shrugs