Milton J Madison has a good roundup of commentary on the arrest of Straits Times journalist Ching Cheong for ’spying.’ He also offers his view:

I think that there are several things going on here. There
is a typical scam involving local officials against foreign Chinese
where they get "caught"/set-up doing something that is somewhat illegal
or accused of doing something illegal. They are then held for ransom
and their loved ones are told not to tell anyone and if they do, then
they will put them on trial for some trumped up charge.
Also,
the mad-mandarins are very concerned with covering up everything that
they can regarding June 4th massacre of innocent students. There must
be something with the transcripts of the late Zhao Ziyang that has
gotten the mandarin’s sphincter muscles a-twitchin’. This sends a very
strong message to domestic and foreign journalists that there is high
price to pay for screwing around with the residents of the fever-swamps
of Beijing.