Contract expiry

After the contract has expired/terminated/completed in Bahrain, what is the process of getting work visa with new employer (job is offered) within 30days.... will there be full medical test again for work permit to be issued?

Contract immaterial. If your work visa has expired or been cancelled or allowed for mobility, new employer can apply for a visa for you.

Thank you. Can the mobility be allowed if visa is expiring in 15 days. How long before expiry is mobility allowed..

No, not allowed.  Permit should be valid for 3 months.