The Democrat Party is expected to nominate former leader Banyat Bantadtan as the House speaker on Thursday after another of its former leaders, Abhisit Vejjajiva, opted out of the race, said a source within the party.
The vote will take place on Saturday.
The source said the Democrat Party has consulted with the Palang Pracharath (PPRP) and Pheu Thai parties on this issue.
If the two largest parties agree to Mr Banyat assuming the role, they will supposedly withdraw their candidates from contention.
PPRP and Pheu Thai have each built their own potential coalition party alliances to form the next government. Their votes will be vital in choosing the new speaker.
However, Pheu Thai has reportedly thrown its hat into the ring to select both the House speaker and two deputies.
Pheu Thai secretary-general Phumtham Wechayachai said party executives would discuss a proposal to go ahead and nominate party MPs to compete for the roles.
The Democrat source insisted the expected decision to nominate Mr Banyat has nothing to do with whether it joins the PPRP in forming the government. Talks on the issue were ongoing, the source added.
However, Mr Banyat's nomination, which could be announced later on Thursday, came after Mr Abhisit declined to be considered for the speaker's role.
Sorasak Pianvech, House of Representatives secretary-general, said all three positions will be decided upon through a secret ballot on Saturday at the TOT Plc auditorium in Bangkok.
Each candidate would require the support of at least 20 fellow MPs to qualify to be compete for the top House role.
Deputy Prime Minister Wissanu Krea-ngam said a new premier will be picked after the three poitions are filled.