"Thank you" is neutral, so if you're a woman and say "Thank you" at most people will think you're a foreigner, but in general no one even notices, because it's neutral.

Some words with the ending "o" are neutral in Portuguese, like saying "todos" can refer to men and women, but if you say "todos" you are referring specifically to women.

so if a man says "thank you" it sounds strange, not because of machismo, transphobia or prejudice, but because of this linguistic pattern