While there has not been an official statement from the Houston Dynamo, based on this tweet by Brad Davis it appears that Michael Chabala is returning to the Houston Dynamo.
The Dynamo drafted the defender in the 4th round of the 2006 MLS SuperDraft, but did not make his MLS debut until 2009 against RedBull New York. Chabala ultimately made 47 appearances for the Dynamo before he was traded to the Portland Timbers in July of 2011. Subsequently, in 2012, Portland traded Chabala to D.C. United, who declined his contract option for 2013.
Since Chabala obtained free agent status after going undrafted in the 2012 re-entry draft, if the Dynamo did sign him, the Dynamo did not have to give anything up to make the deal. In light of that, along with the fact that the Dynamo need back line depth and Chabala is already familiar with Dominic Kinnear's system, this seems like a no-brainer of a preseason signing.
I'll update this as more details become available.