Is tori mandibularis normal? i'm asian..

Yes: Tori mandibularis is fairly common The prevalence ranges from 5% - 40% depending on the population. . Mandibular tori are more common in Asian and Inuit populations, and slightly more common in males.

Common, harmless: Tori mandibularis (see picture) are common and harmless. They are more prevalent among Asians than among Caucasians. http://www.odonti.com/uploads/tx_tjsmarketplace/itmimages/M_WILLARD_00000003_20100714150048.jpg

Not per se ..: It is a phenomenon more common in asians. But it is felt to be somewhat genetic but also related to local stress to the bone in the area of the bony outgrowths; often that stress is related to bruxism(as in clenching of the jaw). Reassuringly these formations rarely cause any issue and limited interventions really ever need to be undertaken. Best of luck.