International travel COVID-19 Passport, Farang 170 baht, Thai 50 baht.

[Rice]

Without being argumentive re: 'dual pricing' ...your Mrs speaks Thai...and she purchased your 'higher priced' "Covid"-passport.

Seriously an overcharge of over US$3..."Where is the justice?"

I'll check in with @Rice as to how being fluent in speaking and reading Thai paves the road ahead with Thai officialdom. (Tongue in cheek per his post above.)

Or are you referring strictly to negotiating rates with a future partner, spouse or one-nighter.
Personally I believe there is "an expectation" [of a higher future gain] on the part of any 'woman'/ partner (Thai and elsewhere throughout the globe) from the westernized male (unless the woman/ partner) is the real breadwinner.
Just my opinion.

But assuredly, let's not go off the topic of your OP. Go to any Thai National Park and see the dual rates for admission...whether one speaks Thai fluently or not.

Speaking Thai has only ever got me in trouble with officialdom. Well they start it most of the time. I have made friends in at least in one government department though.
Believe me, around half of all officials are obnoxious persons that hate their jobs, that they paid for to get. When they deal with a foreigner its a great time to vent abuse. It would be great if I did not understand it. But I do. The other half are decent human beings. On the subject of negotiating rates with a future partner, spouse or one-nighter.
NO COMMENT.

Lets say I could write a book.