No, you can't do an MBA after 12th as it's a master's degree and before a master's one needs to have a bachelor's degree. You can pursue a bachelor's from absolutely any field (Ex: BBA, BTech, BA, etc) and then you can go for an MBA.
Eligibility for MBA Program:
The minimum eligibility criterion for admission is at least a 3-year bachelor's degree with at least 50 percent marks or equivalent (45 percent for SC/ST or persons with disability (PWD) category, of any of the Universities (please check specifications) or possess an equivalent qualification ...
The prospective applicant must satisfy one of the following eligibility criteria for admissions to the MBA program.
A graduate degree under 10+2+3 or 10+2+4 pattern under any discipline, securing at least 50% marks in aggregate, from a recognized university.
An honors degree under 10+2+4 pattern from a recognized university under UGC Act with at least 50% marks in aggregate including languages
Candidates who have passed a Bachelor/Master's degree through correspondence / Open University System from this university or from any other university, recognized by law, are exempted from 10+2 pattern. The duration of the degree program must be 3 + 2 years
Important:
Candidates who pass a bachelor/master's degrees in any university system in single sitting pattern are not eligible for admission to the MBA program offered by AIMS Institutes, Bangalore. In the case of SC / ST / Category I candidates, there is a relaxation of 5% in the aggregate of marks obtained in the University Exams
The MBA admission criteria are based on the valid score of MBA PGCET / CAT / MAT / ATMA or any state-approved admission test.

Thankyou.

Dear student,

You CANNOT go for MBA directly after 12th. MBA is a Master's degree and before pursuing a Master's degree you have to first complete a Bachelor's Degree. After completing Bachelor's Degree (it might be in any field) you can opt for MBA.

I hope it helps.