New appointments will be made to the key finance and defence portfolios, officials said on Wednesday.
Last week, President Salva Kiir sacked the cabinet, Vice President Riek Machar and put his top Sudan negotiator, Pagan Amum, under investigation amid a power struggle.
Dau told Reuters he had been appointed again. "We will try to continue with the same programmes that we laid in the last two years," he said, without elaborating.
The landlocked country plans to build an alternative oil pipeline to Kenya or Djibouti via Ethiopia to end reliance on Sudan. Exports need to go through the former civil war foe, which threatened last month to close two cross-border pipelines unless a row over alleged rebel support is resolved.
South Sudan is also planning to start oil exploration in the Jonglei state with the help of France's Total and U.S. firm Exxon but tribal and rebel violence has made it impossible so far to start work.
Jonglei governor Kuol Manyang, a former civil war commander, said he would become the new defence minister. "I'm happy. It's a challenge, but I think I will manage it," he told Reuters.
The new minister of commerce and economic planning, a new portfolio including the finance ministry, will be Aggrey Tisa Sabuni. He said his biggest challenge will be to balance a budget strained after a 16-month oil shutdown in a row with Sudan, from which the South seceded in 2011.
More names will be announced on Thursday, officials said. Kiir has already appointed Information Minister Barnaba Marial Benjamin as the new foreign minister.
Kiir is facing dissent from inside his party and also some of the general public for failing to deliver on a "peace" development dividend in the war-torn country which seceded from Sudan in 2011 after decades of civil war.
Machar said on Friday he would challenge Kiir for the chairmanship of the ruling Sudan People's Liberation Movement, a contest that analysts fear might threaten the consensus among rival tribes and former civil war militias that holds the vast country together.
Stability in South Sudan is key for crude oil producers from China, India and Malaysia operating in the country and for east African neighbours Ethiopia, Kenya and Uganda which were swamped with refugees during the civil war.