I am a Thai and I understand Loa quite well, I found not any problem while we were talking by our own speeches to one each other. Comparing the southern dialect, The many Bangkokians are more mutual intelligible Lao language than southern Thai dialect. And by the fact, many Laos people speak Bangkok language more beautiful than a lot Thais from the southern provinces.
Thai and Lao Language are very close like German in Germany and Swiss German, not between British English and American English. We both mutual intelligible, but we speak in different tone , some words and little expression.