Will my Thai girlfriend's lack of basic English affect her K1 visa interview with USCIS?

they are more concerned with the relationship than her english ability

make sure she can show photos of you two travelling around, at home, etc documentation of the relationship.

My ex was questioned in

@Th**

.

Is it ur kid? if not keep him FAR out of the picture

I thought for interviews they got interviewed alone.

Her interview will be at the embassy in Thailand to get the visa.

I did this (quite a while back, 2015) and in BKK to get the visa was a breeze. She was offered to answer questions in Thai but she chose English to show she understood.

However, once in Hawaii and we were converting her K1 to her green card (after marriage) that was strictly English and not too friendly.

I would also say for citizenship it should hr better than basic. They asked her quite a few questions on several topics including my work, family, kids, and previous career. It also includes a written and oral test. When we were there I was in the waiting room during her interview and I saw two people that were rejected because their English wasn’t good enough.