Reuters has already reported this, but the Thai government's official twitter account @ThaiKhuFah now tweets:

House dissolution to take place in the first week of May, PM Abhisit announced today.

Section 108 of the 2007 Constitution:

The King has the prerogative to dissolve the House of Representatives for a new election of members of the House.

The dissolution of the House of Representatives shall be made in the form of a Royal Decree in which the day for a new general election must be fixed for not less than forty-five days but not more than sixty days as from the day the House of Representatives has been dissolved and such election day must be the same throughout the Kingdom.

The dissolution of the House of Representatives may be made only once under the same circumstance.

BP: So a late June-early July election.* Now, the fun and games will begin. More analysis in the weeks and months to come.

*Of course, we could have a coup – still unlikely – or Abhisit could be replaced before this – again unlikely.