Flora and Fauna

One of the things I fully expected to happen during our month in Thailand was to explore and experience the local flora and fauna....in my gastrointestinal tract.
Others who have gone before me say it took them a month or so to adjust.

I am known to have an iron stomach like Mikey on the old Life Cereal commercial. Give it to Vince....he'll eat anything.

Lin has been known to open a Mystery meal container in the refrigerator and say...."This smells bad.  Here, taste it."  I can't remember the last time I had food poisoning.

What has happened in Thailand has me a little confused and I would like to hear about other's experiences.

We love street food, cart food, and open air restaurant food.  To be safe we always look for the food vendor who has lots of locals eating there.  This has never failed us. Hey, they aren't going to poison their neighbor, are they?

I have had zero problems with Thai food.  Nary an upset stomach.

What confuses me is that on several occasions, after eating falang food I have felt yucky.  Not sprint to the squatty potty yucky, just blah.

It doesn't happen every time but about 40% of the time.  We have eaten in several places, several times and one time I am fine and the next I feel funky.

Logic would tell me that the Thai food might cause this, but I didn't expect it from the falang food.  Maybe it is a deep seated aversion to falang food.

Is there a food scientist in the house (Where is Alton Brown?) who can make sense of this?