Situation with Thai text on a client site is that we can\'t control where exactly particular words/sentences are going to break between the lines (how web b
The ICU and ICU4J libraries have a dictionary based word break iterator for Thai that you could use on the server side to inject breaking zero width spaces where appropriate.
Or, you could use this to build a utility that could run at build time or on delivery of translations, if you knew the spacing requirements that far in advance.
see ICU Boundary Analysis for more info. These libraries are available for C, C++, and Java.