Well, this is probably the simplest double boiler you can put together using items from Singapore’s HDB shops. Just look around the household essentials stores for a large metal cup (usually used for brewing coffee or making soft-boiled eggs) and a larger bowl, either ceramic or metal.
To melt chocolate, simply fill the metal cup with hot water, or heat the water while the bowl sits on top. Then add the chocolate to the bowl and let it melt slowly.