From a BBC report, 3:55am EDT Aug 30:
Police spokesman Prawut Thavornsiri said the man "is a culprit in the same network" as those behind the blast.
But national police chief Somyot Pumpanmuang downplayed any suggestion that the suspect was connected to terrorism.
"He is a foreigner, but it's unlikely he is an international terrorist. It's a personal feud," Mr Somyot told a televised news conference.
"He got angry on behalf of his friends and family members," he added without elaborating.
Police arrest Erawan bomb suspect (Updated Sunday).
I'm not going to bother to quote the extensive report, which conflicts with other news sources in various details including how the police nabbed the suspect. But this does look like the most informative and authoritative report to be published so far.
A Reuters report filed at 12:07 EDT August 30 adds a few details that can be thrown onto the pile of data bits.