Yes, you can. All Standard Plan coverage (except on psychiatric treatment) is worldwide. Flexi Plans must offer at least Standard Plan level coverage on a worldwide basis, while there can be restrictions on the enhanced coverage by region (e.g. Asia only). In other words, no matter if it is a Standard Plan or Flexi Plan you are holding, you can rest assured that any medical expenses incurred outside Hong Kong will be covered at least to the level of the Standard Plan.
Note that the Supplementary major medical benefit of Flexi Plan (SMM) is restricted to Hong Kong, while the "Full compensation" benefits of Flexi Plan (Superior) are restricted to Asia (including Australia and New Zealand). Refer to the brochure for more detailed explanation.