I find that the Garlic here in Northern Thailand is very mild. Can one buy a stronger tasting Garlic here or do I have to make do with what they have in Tesco and Macro?

Depends where you are. Last week I bought a kilo on the road side between Nakhon Phanom & That Phanom. It was only 60thb and the sack read "Grown in China" -- OMG, what next?. And yes it was as moist & as pungent and on a par with the best French garlic I remember from decades ago.

Thanks, I'll keep out a watch for Chinese Garlic.

Why don't you just use more of it?

Thanks, I'll keep out a watch for Chinese Garlic.

They are not strong, you can try the small Thai garlic sold at markets.

Semper is correct; don't go for the large but for the small garlic sold on the markets. Check that the garlic balls are hard and firm. Don't keep garlic/onions in the fridge.