My spiciness register has dropped through the years, so I now get Americanized dishes.
To me the test of a good to great restaurant is how they cook Tom Kha Gai soup. Tried it all over and have realized that my preferences have drifted away from what is the Thai standard - but I like what I like, so there.
Most Thai restaurants are very careful about ingredients, at least in Texas. I find that the quality drops along the East Coast, and that the West Coast is hit or miss.
Recipes and the skill of the owner/head chef truly make the difference.
So what does one look for in Tom Kha Gai soup to discern good or bad?
Tom kha gai is my favourite Thai dish, and it’s my barometer, just like you. It’s a delicate soup, so balance of flavours is essential. I’ve lived more than half my life in S.E. Asia, so I feel that I’m a fair food critic.