Can I renew my non-immigrant o visa(married) in Singapore. My visa is multiple entry and can I get one from the Thai embassy in Singapore?

If you have marriage certificate and copy of spouse ID card you should be able to obtain a non immigrant O visa in Singapore (paying for it). If you also can show a bank account with more than 400k value you may be able to obtain another multi entry.

I assume your visa has expired and you are completing the last 90 day entry (permitted to stay stamp)? If visa has not expired you can exit/return for another 90 day stay.

If you have marriage certificate and copy of spouse ID card you should be able to obtain a non immigrant O visa in Singapore (paying for it). If you also can show a bank account with more than 400k value you may be able to obtain another multi entry.

I assume your visa has expired and you are completing the last 90 day entry (permitted to stay stamp)? If visa has not expired you can exit/return for another 90 day stay.

Is it ok for me to obtain a multi entry visa without 400k in the bank; as I did in penang 13 moths ago?

Do not believe you have much chance.