Honestly I haven't really experienced this issue in Thailand IRL (except from hate posts on this forum) except for some funny (what are you?) looks at Arabic and Iranian restaurants. That could be about being western or American anyway. People who deny that many people do look and act ethnically Jewy to varying degrees even without wearing stars or skullcaps are really very clueless and ignorant. Jewish people understand that there is a range for that (like from could be a blonde Aryan Hitler Yugend to Woody Allen/Sarah Silverman). I'm somewhat in the middle, so ambiguous, so yes can be taken for some kind of "Mediterranean" or Middle Eastern. Hilariously there are many non-Jews that present as very ethnically Jewish. Also many non-Jewish New Yorkers sound as if they're Jewish. My context for ethnically Jewish is mostly in the American context (so mostly Ashkenazi) so there is even more to this than meets the eye.
OK, I did have one uncomfortable experience with an Iranian restaurant I used to go to fairly often, but again this could have been about being western, but I'm sure being a western Jew would have been a bonus. The restauranteur was always trying to get me to talk about my nationality and I dodged the question repeatedly which of course he noticed. I don't want Iranian cooks to know too much but with buffets there are no worries. To people who say that's paranoid, you're wrong. I got a hostile feeling from that guy.
On another occasion I did say I was American to a young Iranian server AFTER the food was served. I just got a positive vibe from him and it turned out I was right,. But generally don't ask, don't tell can be the sensible way to go.