PPP spokesman Kudep Saikrajang quoted Somchai as telling the PPP executives that he is ready to be prime minister and solve the country's problems.
The decision at the meeting of PPP executive board on Monday morning.
After two-hour meeting, Kudep said the board will inform the PPP general meeting at about 2pm.
However it seemed that some factions in the party did not agree with the decision.
Songsak Thongsri, an MP, a member of so-called Friends of Newin faction, said that he could not accept the decision because some executive members have no chance to debate whether Somchai is the best candidate.
The Parliamnet is scheduled to meet on Wednesday to choose the new prime minister, replacing Samak Sundaravej whom the Constitution Court disqualified for violating the charter.