My wife and I currently have a joint account in a Thai bank, the total of which easily covers the equivalent of 1,600,000 baht that is necessary to get our O-A retirement visas. However, will the immigration department accept this type of account, even if we go to the immigration office together to get our visas, or is it better to split the account into two, with one in each of our names?

It would probably be best to have separate accounts if it does not cause a 3 month rule problem for you. If it does you can try to use the joint account.

Edit: You say OA so perhaps you are talking about a visa issued in the UK rather than doing it it Thailand. In that case only the Embassy can answer you but suspect they would accept it.

My wife and I currently have a joint account in a Thai bank, the total of which easily covers the equivalent of 1,600,000 baht that is necessary to get our O-A retirement visas. However, will the immigration department accept this type of account, even if we go to the immigration office together to get our visas, or is it better to split the account into two, with one in each of our names?

We were able to use a Joint account to get our retirement Visas. You will need to bring a copy of your marriage certificate.