We went to Nakorn Nayok immigration office. We are so confused. We went 3 times, Each immigration officer told us they needed different documents for the same extension. We just need a 4 day extension on a 60 day tourist visa. The officer there wanted us to pay 2500 bhat each and she would grant it right then. She said if we only have her 1900bhat she would have it sent off and it would be back in 2 weeks. Online is says 1900bhat. We are staying the 4 extra days because of a medical condition and the doctors advice.
Should we just pay the fine upon leaving with the letter from the hospital, or go to the immigration office in Bkk? Any recommendations?
We were told it was in the discretion of the immigration officer whether or not to grant us the extension for four days. She said the price might go up. Would it hurt us if we had a letter from the hospital stating I am having surgery on the 8th? If we gave that at the time of exit, would it hurt us? 
TLDR : Answer Summary
The user is seeking advice on obtaining a 4-day extension for their 60-day tourist visa due to a medical condition. They have visited the immigration office multiple times, each time receiving conflicting information regarding the required documents and fees. The initial fee quoted was 1,900 baht, but an officer demanded 2,500 baht for immediate processing. The user is contemplating whether to pay the fine upon departure with a hospital letter or to continue pursuing the extension at the immigration office in Bangkok. Comments from other users indicate that a simple request for a 30-day extension should suffice, and they advise against mentioning medical reasons, as it may complicate the process.