Try a mouthwash of Citricidal grape fruit seed extract but be careful with it. It’s strong stuff and there is a good deal of literature available that suggests it’s active ingredient is in fact synthetically added Benzethonium Chloride, which is highly, highly toxic and is not approved for human consumption in Europe or the USA.
However, when used diluted as per the packet instructions I think it’s the most effective short term anti-fungal. I have used it against colds, sore throats, oral thrush, stomach parasites and a few bad attacks of candidiasis for about 15 years and I’m OK. I am prepared to risk taking something poisonous and unnatural if it kills the symptoms quickly when used with caution (don’t exceed the concentration/dosage on the packet). I imagine it’s bad for your tooth enamel as well, so if it’s not working within a day or two, give up on it.
For longer term anti-fungal (and in addition to the citricidal) swallowing coconut oil and garlic should be helpful. Swilling olive oil round your mouth has a temporary effect on oral thrush and should stop it growing.
The main thing is that you need to give up smoking -if you’re still smoking, that is probably the immediate cause of your problem and the reason it does not respond to mouthwash etc. Also take sugar out of your diet immediately.