Credit Suisse CEO Tidjane Thiam will deliver his final earnings report at the helm of the Swiss lender on Thursday, less than a week after his resignation was announced.

Thiam's departure comes amid an investigation by Swiss regulator FINMA following two instances of former Credit Suisse employees, including former wealth management boss Iqbal Khan, being placed under surveillance.

The outgoing CEO has maintained that he was not aware of the spying operation, which led to the resignation of COO Pierre-Olivier Bouee and the suicide of a private investigator, prompting concerns over how both Thiam and Chairman Urs Rohner were kept out of the loop.

Bruno Verstraete, partner at Zurich-based asset manager Lakefield Partners, said the timing of Thiam's ouster had come as a surprise, and suggested that an acceleration of the FINMA investigation could have been the catalyst.

"This spying scandal has gone on for months and what we are seeing is that after the weekend the storm has not really receded, in fact quite the contrary," Verstraete told CNBC's "Squawk Box Europe."

"It looks as if the pressure now is away from Thiam, who has a good leaver agreement with the bank, and that the pressure is now on the highest organ of the company, which is Rohner."