I have completed a discussed with the management and would like to inform you that your requested was considered to be unacceptable. Our management would like to keep the rental rate of Baht 790/sq.m./month and offer One (1) month Rent Fee for compensate the renewal rate. 
The renewal rate that offer to your client is a special price and lower than other tenant. 
Please inform your client, if your client accepts this condition I will arrange for the new version offer letter. 
Thank you & Regards,