@Brandon ***********
is absolutely correct.
Medical extension is impossible to get.
I have had personal experience of this.
Immigration do not care, unless you are half dead, on a ventilator or unconcious in a hospital you won't get medical extension.
I had ACDF Anterior Cervical Disc Fusion (spine surgery) at Bangkok Hospital, personal expense 700'000bt.
I was in agony, incapacitated, had all documents from hospital and doctors.
Immigration officers are hard hearted and hard headed unsympathetic people.
They declined any medical extension.