I think that they’re as illegal as they are in the US, not more. I think it’s perfectly fine to “cold-call” people but then you’re not allowed to send more emails unless they subscribe or respond.
In reality it’s very easy to end up subscribing to newsletters and even my European embassy subscribed me to their event newsletter in Thailand—of course I never agreed to any of that.
That’s not accurate. If your email is on your website, of course they can email you. If what you said was true in absolute terms, communication would be impossible.
They can contact you for legitimate reasons, which could be "hey, your website has content from me that is copyrighted" they can't contact you for sales reasons without your consent.
In reality it’s very easy to end up subscribing to newsletters and even my European embassy subscribed me to their event newsletter in Thailand—of course I never agreed to any of that.