Prasert also stepped down as chairman of Bangkok Dusit, Thailand's largest hospital network, and vice chairman of Bangkok Airways, the companies said in separate statements.
Late on Friday, the Securities and Exchange Commission of Thailand said Prasert, his daughter Poramaporn and another executive Narumon Chainaknan executed and matched trading in Bangkok Airways shares between Nov 2015 and Jan 2016 that caused price and volume to be inconsistent with market conditions.
They were fined 499.45 million baht ($15.75 million) and barred from holding directorships and executive positions in listed companies. Poramaporn, chief operating officer at Bangkok Dusit, and Narumon, executive secretary to the CEO of Bangkok Airways, also resigned from their positions on Monday.
The accused will "prove their innocence in the matter", the companies said.
Currently, Prasert holds 18.4 percent of Bangkok Dusit and nearly 6 percent in Bangkok Airways, while Poramaporn, has a 6.49 percent stake in the boutique airline, according to Refinitiv data.
Bangkok Airways shares fell more than 5 percent while Bangkok Dusit slid 7 percent on Monday morning.
($1 = 31.7200 baht)
(Reporting by Chayut Setboonsarng; Editing by Muralikumar Anantharaman)