How do I prove adequate funds for tourist visa?

I have a Thai bank account, but I assume its a bad idea to use a statement from a Thai bank as proof of funds for a tourist visa?
Can I just show them that I have the required amount in cash?
Also, on the application form,what do I use as Date of previous visit to Thailand?
The last date I left Thailand, or the date I entered? I think I have used the date of entry in the past without being questioned about it, but that may not be correct.