In North America, there's a product called CLR for clearing mineral deposits on appliances and inside pipes.

It stands for "calcium, lime, & rust" and I've found it very effective and easy to use.

I've checked their website, and it looks as if this product is only available in North America.

Anything similar that one knows of that can be bought in HomePro or Siam Global, etc?

Try Vinegar.

The materials data sheet http://www.jelmar.com/msds/2013/CLR_SDS_521213%20.pdf suggests it's a mild acid and surfactant (soap).

Vinegar and washing-up liquid perhaps?

I've used vinegar and found it only mildly effective. I can soak a shower head in it for several hours and see just a slight improvement.

However, put a similarly mineralized item in CLR and one can actually see it bubbling, and the minerals just wash away.

I'd like to use it on faucets, and particularly in my shower, on the head and hoses, and even try to see about pushing some into the heating tubes to ensure they're clear and open for full flow.

HomePro in Udon has a similar product. I have used it it and it works. Found with other cleaning products. I don't bother to ask. I just wander around and look. You probably won't get an answer anyhow.

HG Professional lime scale remover. Comes in a 1 liter bottle that you mix with water up to 1:10. For Plastic 50/50 would be good. I use it for everything. Full strength in the toilet. Guess at how much water is in the toilet.

They also have one that comes premixed in a spray bottle for cleaning showers and sinks.

I think they carry it at the Amway outlets and via Amway sales person - I think I saw it there so time ago.