Sompong Amornwiwat is expected to retain the leadership of Pheu Thai, a party source said on Wednesday.
The source said the party had decided that the former Chiang Mai MP should take the helm.
The decision will be formalised when the party general assembly meets on Thursday to select its leader and executive members.
Mr Sompong resigned on Saturday after chief strategist Sudarat Keyuraphan and her team announced they were quitting their posts, but still staying with the party.
The source said Pheu Thai will slash the number of deputy leaders by more than 50% -- from 15 in the previous line-up to seven -- but all factions would still be represented.
Prasert Chanruagnthong, an MP for Nakhon Ratchasima, would be elected the party secretary-general, the position held by Anudit Nakornthap, the source added.
Aruneee Kasayanond will replace Anusorn Iamsa-ard as the new spokeswoman, according to the source.