Applying for second tourist visa to China

Yes, it's ok to provide an invitation letter from the foreigners in PRC. The invitation letter should contain:
1. information about the applicant: full name, gender, DOB etc.
2. information about the planned visit (arrival and departure dates, places to visit, etc)
3. information about the inviter: name, contact telephone number, address and the signature.

Besides, copies of the inviter's passport and legal residence permit (if necessary) are also required.