Men - (dare I add, in particular farang men) are bound to 'see' more women than men out and about. Just as women would clock more men!
I also always thought that birthrates worldwide tend to be slightly higher numbers of girls to boys, simply because thats what nature intended for the survival of the human race?
But if simple observation in a town like HH has produced a 3/4 to 1 ratio there are many explanations. Some already mentioned, like the number of Thai men who are in temples, or the services, or simply away working.
But in places like HH there is the other factor. Men stay away to allow their women to get on with the business of fleecing farangs.

Sorry guys - it had to be said.
Meanwhile Sarges' first - and very pertinent - question has largely been overlooked. I.E how would a 3/4 to 1 ratio affect culture, politics and attitudes in our own countries.
Well I guess women would see their way clear to become politicians, scientists and engineers on the basis of merit, rather than the need to fill female quotas. They would be even less picky in their choice of men, and probably decide to marry in even less numbers. But they would demand high class IVF sperm from an ever decreasing decent gene pool to father children which would be brought up by an increasing number of single Mums. Meanwhile women would of course continue to do all the things they usually do, like going out to do the shopping (and be head counted in the process.)
Overall then not a lot would change.