Not from Singapore, but I play in the OCE region regardless. In Sydney servers, you can't really get 5-10 pingers with normal NBN wifi, and is only really accessible via ethernet.
I play regularly at a Chinese PC Cafes, and i get 5-10 ping consistently most of the time. The point I am trying to put forward is that alot of 5-10 pingers are playing from an internet cafe, as such a ping is rarely accessible at home.
Most of the time if I get a 5-10 pinger on my team (and yes, i am about the same rank as you), they are usually a Chinese person playing at an internet cafe. So, I suppose you can assume that the same can exist in Singapore servers.
So I suppose you can assume that a 5-10 pinger in Singapore would have the implications that you have pointed out above. But personally, I really just think that you've just been getting unlucky. Surely not every 5-10 pinger Singaporean is toxic and annoying.
Discord