Will be unreliable from the start. The outcome of a survey is effected by where it is done, how it is done, and in Richard's case especially by who it is done. They will all tell him they prefer a farang (if they do not Richard will lose face!), but if the poo yai baan conducts the same survey they will all prefer a Thai men.
I remember a "field study" (I think that was Richard too) regarding preferred nationalities. Believe me, the women really cannot be bothered with your nationality as long as all their financial needs are paid for. Of course there is always this one girl that really (dis)likes Germans, Dutch, Swedes, English or whatever nationality, most of the time based on a single personal (good/bad) experience.
And of course many professionals know that the average farang likes to hear that all Thai men are pretty much worthless, and that the English like to hear that all Germans are rude and overweight, and the Germans like to hear that the French are not showering and avaricious, and the French like to hear that the English are always drunk, noisy and looking for bar fights with their football shirts tied up around their waist.
I from my personal experience however know at least one German who is very polite, one Frenchman who does not smell and bleive it or not even an Englishman who is not drunk all the time.

We are all living in 'the good old days' of the future.