Chainrai, through his company Portpin, has re-entered the equation as a bidder for the League One club.
Just eight days ago Portpin announced its interest in buying Portsmouth, who remain in administration, was at an end.
That appeared to leave the Pompey Supporters Trust (PST) offering the club's last hope of survival.
Hong Kong businessman Chainrai's company remains Portsmouth's biggest creditor and the PST urged him to negotiate with them over the value of the club's stadium, Fratton Park.
That remained a sticking point, and now Chainrai and Portpin are confident of reclaiming control of the troubled club, averting possible closure.
If Portpin proceed, and have the backing of administrator Trevor Birch, they could scupper the supporters' hopes of bringing the former Premier League club under their own control.
A statement from Portpin said: "After many discussions with the related parties, including amongst others, the administrator, the Football League, the PFA, and officials from Portsmouth City Council, Portpin Ltd announces that it has decided to take action in order to avoid the imminent liquidation of Portsmouth FC.
"Portpin's offer will be in much the same form as previously with the club's current CVA being honoured and football creditors being settled in accordance with current agreements.
"Under Football League rules, the satisfactory treatment of football creditor obligations is critical to the financial eco-system of all members of the Football League.
"Although Portpin positively viewed takeover interest by the Portsmouth Supporters Trust, we understood from the administrator that the terms offered by PST were problematic in two areas - the further reduction in football creditor debt to ?2million and the uncertainty of the committed capital raised and held in escrow to both fund the takeover of the business and to provide guarantees for the next three years' cash flow.
"We hope to finalise this transaction in the next two weeks.
"Portpin is taking this step to save the club and will look to continue to work with interested parties - including the Portsmouth Supporters Trust - to ensure that the club will have a sound business foundation to enable it to remain financially over the long term.
"We hope everybody including the huge fan base will support this saving process."
When Portpin pulled out initially, Chainrai listed a number of reasons behind his decision, most notably a lack of support and co-operation from administrator PKF and other involved parties.