Law and Cheung, who are charged with "collusion with a foreign country or with external elements to endanger national security" appeared at the West Kowloon Magistrates' Courts on Saturday and were denied bail by Judge Victor So.
They will next appear in court on August 13.
The pair are accused of colluding with Apple Daily owner and staunch Beijing critic Jimmy Lai between July 1 2020 and April 3 April 2021 to request a foreign country, person or organisation "to impose sanctions or blockade or engage in other hostile activities against the Hong Kong Special Administrative Region or the People's Republic of China," according to a charge sheet.
The National Security Law came into force in Hong Kong just before midnight on June 30, 2020.
Judge So said Law and Cheung were denied bail because there was insufficient evidence to believe they would not endanger national security.
Under the security law, the onus is on defendants to prove they will not pose a security threat if released on bail.
Three companies related to Apple Daily that are also being prosecuted for collusion with a foreign country appointed people to represent them in court. Authorities have frozen HK$18 million ($2.32 million) of the companies' assets.
The other three executives arrested on Thursday, Chief Operating Officer Chow Tat-kuen, Deputy Chief Editor Chan Puiman and Chief Executive Editor Cheung Chi-wai, were released on bail late on Friday, according to Apple Daily.
Earlier on Saturday, crowds had gathered outside the court ahead of the hearing, some holding yellow umbrellas or wearing Apple Daily T-shirts saying, "No fear, fight on."
"Right now, you can be charged with NSL (the national security law) because of a word or a speech that they didn't like. It’s a big regression,” Lo, 29, a reader of the popular, 26-year-old paper, said.
The law punishes what Beijing broadly refers to as secession, subversion, terrorism and collusion with foreign forces with up to life in prison.
The arrests and scale of the Apple Daily raid have been criticised by Western nations, global rights groups, press associations and the chief U.N. spokesperson for human rights.
Apple Daily and its listed publisher Next Digital have come under increasing pressure since Lai was arrested last year under the legislation.
Lai, whose assets have been frozen under the security law, is already in jail for taking part in unauthorised assemblies and awaiting trial in his national security case.
As investigations into Apple Daily and its senior executives ramp up, some employees and observers have expressed deepening concern over the newspaper's future.
Since the law was imposed by Beijing in June last year, more than 100 people have been arrested, with most denied bail.
(Reporting By Jessie Pang; Writing by Anne Marie Roantree; Editing by Alun John, Shri Navaratnam and Raju Gopalakrishnan) ((firstname.lastname@example.org; +852 97387151; Reuters Messaging: email@example.com))