Quite agree with you Archie. Unfortunately I seem to encounter a number of the types you describe.
I recently decided to have an apple pie and afternoon drink at a local eatery. So I am sat down eating said pie, with a drink, and watching a replay of the weekend's F1 on the TV behind the bar. Along comes a fellow countryman farang, plonks himself down in the very seat right next to me, buys some cigarettes and then lights one up.

I got up and moved to the bar and finished my food & drink and then promptly left. I didn't say anything to him, as we were sat outside rather than inside. Nevertheless I consider it gross bad manners. Even before the law changed in the UK it would have been considered most impolite to smoke near anyone eating.
Second example, I am sitting in(side) a bar in town having a quiet beer, when in comes another farang, sits smack bang in front of/opposite me (less than 1m away), and lights up a cigarette.

I got up and went & sat outside until I had finished my beer and then promptly left. Judging by the behaviour of the staff in that bar, and the fact that at least 2 of the 3 were smokers, I think the irony of the situation and the fact that they lost a customer would not have dawned on them.
I despair that some of the farang smokers are even aware of their gross bad manners, and the non-smoking law is not enforced around here.