If you ask for meter they say yes ok.
When you start going you still need to remind him because if you forget he will not always put it on.
Once we took a taxi and it was about 110 baht.
When we got out he said 200 baht and I said it's 110 baht but wife paid and didn't get change .
He just drove off .
Not worth getting 10 of his friends to jump on your head but annoying as fu7k.
I tend to avoid Bangkok unless I have to go.