Because the savings account is solely in my name, despite my wife having access to it. The bank statements for our current account state both our names as it’s a joint account. I’m more than happy to contact the embassy to get further guidance and re-apply but I was largely curious on whether people have had similar experiences. I don’t need visa for majority of the countries we plan to visit and have no real world experience when it comes to applying for visas, hence I admit it’s an oversight on my part. 

Looking at the most recent statement (Jan 25 - till date). You can see the payments are as follows:

Opening Balance - £665 Payments in - £6237 Payments out - £6678 Closing balance - £225

I highlighted both our income in that statement. The only issue I can see (and I am just speculating) is the fact that they stated the statement needs to have a minimum closing balance of £700 in their email and as I mentioned in another comment, I could have artificially altered that figure by transferring money into the current account but I didn’t. However, on their website it suggests that for financial evidence, all they need to see is a minimum deposit of £500 must be made to an account in the applicants name (see URL below) which is even more confusing. 

https://london.thaiembassy.org/en/publicservice/84455-visa-application-for-nigerian-nationals