This has nothing to do with the Android "Ice Cream Sandwich" mobile operating system developed by Google.

In 2015, the national postal service providers of both countries, Singapore Post and Thailand Post issued a joint stamp issue to mark the 50th anniversary of Singapore-Thailand diplomatic relations. The stamps were designed by Singapore's Wong Wui Kong and Thailand's Euamporn Supharoekchai and both feature traditional desserts: Thailand’s mango sticky rice and Singapore’s ice cream sandwich! A set of two stamps cost SGD 2.30.
Both are delicious but I will focus on the ice cream sandwich because the day I am writing this is a sweltering hot day. I did a post on ice cream before in the past, but this is a different kind. FYI the mango sticky rice (or Thai: kao neow mamuang) is served warm or at room temperature.
The main image in the Wikipedia article for “Ice cream sandwich” is this:

But the Singaporean version is very different. For starters, it doesn’t use a hard cookie / biscuit / wafer shell. The recipe is simple: 🍨 + 🍞 = ice cream sandwich!
Instead of putting rounded scoops of ice cream on a cone, the ice cream in a Singapore ice cream sandwich is cut as individual block portions. Then, the slab is wrapped in a slice of bread. Since bread is softer than a cone, the melting ice-cream will dissolve into it quicker.
There are different kinds of bread used, the most popular one is the multi-colored rainbow sliced bread. Technically, only a single piece of bread is used, wrapped around the ice cream slab, so it arguably doesn’t fulfill the definition of a sandwich.
Here’s what it looks like and here are the common flavors sold:

Not a promo. You serve and hold it like a taco or hot dog. Flavors are quite localized, with the exception of raspberry ripple. [Image Source]
Singapore isn’t the only place that serves their ice cream sandwich with bread. Vietnam has bánh mì kẹp kem which are basically scoops of ice cream inside a bánh mì, topped with crushed peanuts.

Also a street food. Almost all the good stuff in Vietnam is anyway. [Image Source]
The Philippines has ice cream on pan de sal (Filipino bread rolls). The violet ice cream below is ube (purple yam) flavored and is a Filipino ice cream flavor. Ube shows up in a lot of other Filipino desserts too.
Everything looks good and you can’t botch up ice cream — it’s just not possible. “You can't buy happiness, but you can buy ice cream, and that's kind of the same thing.”
References:
“Singapore-Thailand Joint Stamp Issue Sweet Delights to Celebrate 50 Years of Strong Diplomatic Relations.” Singapore-Thailand Joint Stamp Issue Sweet Delights to Celebrate 50 Years of Strong Diplomatic Relations | Singapore Post, Singapore Post, 17 Sept. 2015, www.singpost.com/about-us/news-releases/singapore-thailand-joint-stamp-issue-sweet-delights-celebrate-50-years-strong-diplomatic-relations.