The ThaiAnalyzer/ThaiWordFilter depends on the fact that BreakIterator.getWordInstance(new Locale("th")) returns a dictionary-based break iterator that can segment thai phrases into words (it does not use whitespace).
But this is non-standard that the JRE will specialize this locale in this way, its nice, but you can't depend on it.
For example, if you are running on IBM JRE, this analyzer/wordfilter is completely "broken" in the sense it won't do what it claims to do.
At the minimum, we need to document this and suggest users look at ICUTokenizer for thai, which always has this breakiterator and is not jre-dependent.
Better, would be to check statically that the thing actually works.
when creating a new ThaiWordFilter we could clone() the BreakIterator, which is often cheaper than making a new one anyway.
we could throw an exception, if its not supported, and add a boolean so the user knows it works.
and we could refer to this boolean with Assert.assume in its tests.