Forms 10-Q and 6-K : Companies are required to submit these forms for interim periods (quarterly for US companies on Form 10-Q, and semiannually for many non-US companies on Form 6-K).
There are some exemptions.
It’s compulsory for those foreign private issuers who aren’t exempt
Form 6-k
In the instructions
A. Rule as to Use of Form 6-K.
This form shall be used by foreign private issuers which are required to furnish reports
pursuant to Rule 13a-16 or 15d-16 under the Securities Exchange Act of 1934.
so next you need to find out what a foreign private issuer is, and what Rules 13a-16 and 15d-16 say
Definition of foreign private issuer
If you look up Rule 13a-16 and Rule 15d-16 there are a series of exemptions to the requirement