Analysis of information sources in references of the Wikipedia article "LaTeX" in Chinese language version.
TeX is usually pronounced tech, making lah-tech, lah-tech, and lay-tech the logical choices; but language is not always logical, so lay-tecks is also possible.
LaTeX, which is pronounced «Lah-tech» or «Lay-tech» (to rhyme with «blech» or «Bertolt Brecht»)
LaTeX, which is pronounced «Lah-tech» or «Lay-tech» (to rhyme with «blech» or «Bertolt Brecht»)