The Thai-to-Lao translation capability in Lao Script for Windows is an optional feature available to licensed users.
Since Thai and Lao are closely related languages, and grammatically very similar, it is possible for understandable translation to be achieved simply by using word substitution. If a single document is translated automatically, the result may not be very good, but when a large work is being translated, particularly on a technical subject, it is possible to quite quickly build a dictionary of equivalent Lao words for each Thai word encountered, and use this dictionary to produce quite an acceptable translation. Any words not in the dictionary will be transliterated on a syllable-by-syllable basis, which in most instances will be understandable in Lao.
Often, there will be several possible Lao words for a given Thai word, so to get the best result, the user must select the appropriate word from the given list. Some final editing of the result is usually necessary, but typically only a few words for each page of translated material.
Literary and poetic works, of course, are not likely to be adequately translated by any machine translation approach.