Can I still apply for my visa if I missed a 65k payment but have 800k saved four months prior?

Read the rules

Its ok when you forgot. My extention is always in februari. So need papers from my government. Need to send then my annual income but I get that to late.

So I asked Immigration. They understand

you have two options: quickly park the required minimum of 800,000 THB in your account, or pay an agent and experience trouble to get away from the agent in the following years, because using an agent who will remove the money within 10 minutes, will result in you violating the upkeep rule of the deposit in the rest of the year. Understand? And you will be faced with the same problem when putting your own 800,000 THB into your account - you will be confronted with the same stance: before you can switch back to the 12-months transfer method, to need to follow the rules for the upkeep of the 800K deposit for a full year

My last visa I had to keep my B800k for four months after the new extension, then you can reduce for 6 months to B400k definitely need the full amount two months before renewal. Last time immigration added this information in my passport

I switched from my pension income to 800k and had to provide a copy of my pension income from the previous year in addition to the necessary documents.

Nobody needs to pay an agent, there are ways and means [get ready for the "I value my time" brigade responses 555]

I would say that's ok assuming your last extension was also based on monthly transfers. If it was based on 800k you would need to have met the terms of that extension