He consulted the Parliament legal team before announcing his decision to a press conference on Tuesday.
He called on the Democrat MPs to file accompanying documents to support the no-confidence motion by 4.30 on Thursday afternoon.
Somsak was asked if the prime minister could still dissolve the House after the opposition submitted the censure motion last Friday.
“The PM would not dissolve the House. She said she had no plans to do that,” he replied.
Meanwhile, Chief Opposition whip Jurin Laksanavisit said that the motion seeking a no-confidence debate against the government, which was submitted by 146 MPs last Friday, was complete because it met Constitutional and Parliament rules.
Jurin insisted the opposition had never before had to clarify accusations in a censure motion. He referred to the three last censor motions in 2002, 2003 and 2013.