This is makeindex, version 2.15 [TeX Live 2019] (kpathsea + Thai support).
Scanning input file vocabindex.idx....done (1 entries accepted, 0 rejected).
Sorting entries...done (0 comparisons).
Generating output file vocabindex.ind....done (5 lines written, 0 warnings).
Output written in vocabindex.ind.
Transcript written in vocabindex.ilg.