I speak with my GF in Thai. She understands me perfectly, because she is so used to my mode of speech.
I get some Thais who understand me, others who don't. I accept I will never be fluent, it doesn't worry me. The tones are just too difficult without years of practice.
With the Thais that don't understand me, I call my GF on my mobile, she then gets the message across.
When you've got a language where the word for knee, rice and the color white all sound the same.....there are dozens of examples like that.