Requirement for multiple entries 6-month or more tourist visa

Hello,
I am a French student currently living in Seoul and my boyfriend lives in Shanghai. I was wondering if it was possible to get a multiple-entry tourist visa that lasts at least 6 months to avoid asking for a new visa every month. What are the requirements? Is it OK if I apply today and only have flight tickets for a weekend in February? Will they ask for any other documents?
Thank you for your help. Kind regards,
Melanie