I had the 800,000 baht in an individual account. I accidentally put some of it into an joint account in June. Half of that account was over 1,000,000 baht. I also had two individual accounts with smaller amounts(100,000 - 200,000).

I'm on a border entry from chong mek now. I would like to get a retitrmeny visa. If I go for a retirement visa at immigration Pibun what visa do I ask for? Will they calculate half of the joint account for my money requirements.

You will not get visa or extension of stay at immigration in Phibun if all you have is a visa exempt entry.

If you have a non immigrant visa entry you could apply for an extension of stay. The might accept a total of 800k in all your accounts if the funds have been there for 60 days and you have a bank letter for each account,

In order to get a non immigrant visa you would have to go to Bangkok or go to the consulate in Savannkhet Laos for a non-o visa.

If you cannot apply for the extension because you do not have a visa you should move your funds into one account in your name only.