indicim.jar and thaiim.jar are currently shipped with the JRE but they are sample and unsupported interface mentioned in the article:

http://java.sun.com/products/jfc/tsc/articles/InputMethod/inputmethod.html

Demo or samples seems to be a better place for these sample input methods instead of the JRE.

For example, <JDK>/demo/jfc/CodePointIM is another sample input method.